**Tire Pressure Monitoring and Maintenance Systems Performance Report**

Task Order 8 of the

Commercial Vehicle Safety Technology Diagnostics

and Performance Enhancement Program

![](media/image1.png){width="2.6638888888888888in"
height="0.8638888888888889in"} January 2007

Foreword

This project is one of several performed under the provisions of Section
5117 of the Transportation Equity Act of the 21st Century (TEA-21). The
primary objective of this project was to explore the performance of
commercial vehicle tire pressure monitoring and maintenance systems. The
work performed under the project included:

-   Conducting a market study to identify and select commercially
    available tire pressure monitoring and maintenance systems for
    testing.

-   Developing a test matrix and test procedures to profile the
    performance and operation of the selected systems.

-   Installing selected systems on representative tractor-trailer and
    motorcoach test vehicles, along with a robust instrumentation system
    for collecting and recording test data.

-   Performing testing on a high-speed test track.

-   Analyzing test data.

-   Presenting research findings at a public forum.

-   Developing a report detailing the results of the data analysis,
    observations, and conclusions (this document).

The study focused on commercially available tire pressure monitoring and
maintenance systems. This information should prove useful to motor
carriers in evaluating the capabilities and limitations of these
systems. The findings should also be helpful to the systems'
manufacturers and suppliers. This is the final report of the study
performed under Task Order 8 of a multi-task research contract and does
not supersede an earlier report on the subject.

Notice

This document is disseminated under the sponsorship of the U.S.
Department of Transportation in the interest of information exchange.
The U.S. Government assumes no liability for its contents or use
thereof.

The contents of this report reflect the views of the contractor who is
responsible for the accuracy of the data presented herein. The contents
do not necessarily reflect the official policy of the U.S. Department of
Transportation.

This report does not constitute a standard, specification, or
regulation.

The U.S. Government does not endorse products or manufacturers named
herein. Trade or manufacturers' names appear herein only because they
are considered essential to the objective of this document.

Technical Report Documentation Page

+--------------------+---+----------+---------+---+---------+----------+
| 1\. Report No.     | 2 |          |         | 3 |         |          |
|                    | \ |          |         | \ |         |          |
| FMCSA-PSV-07-001   | . |          |         | . |         |          |
|                    | G |          |         | R |         |          |
|                    | o |          |         | e |         |          |
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|                    | o |          |         | o |         |          |
|                    | . |          |         | . |         |          |
+--------------------+---+----------+---------+---+---------+----------+
| 4\. Title and      |   |          |         | 5 |         |          |
| Subtitle           |   |          |         | \ |         |          |
|                    |   |          |         | . |         |          |
| Tire Pressure      |   |          |         | R |         |          |
| Monitoring and     |   |          |         | e |         |          |
| Maintenance        |   |          |         | p |         |          |
| Systems            |   |          |         | o |         |          |
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|                    |   |          |         | 7 |         |          |
+--------------------+---+----------+---------+---+---------+----------+
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+--------------------+---+----------+---------+---+---------+----------+
| 7\. Author(s)      |   |          |         | 8 |         |          |
|                    |   |          |         | \ |         |          |
| Stephen Brady,     |   |          |         | . |         |          |
| Brian Nicosia,     |   |          |         | P |         |          |
| Robert Kreeb (Booz |   |          |         | e |         |          |
| Allen Hamilton),   |   |          |         | r |         |          |
| Peggy Fisher Fleet |   |          |         | f |         |          |
| Tire Consulting    |   |          |         | o |         |          |
|                    |   |          |         | r |         |          |
|                    |   |          |         | m |         |          |
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|                    |   |          |         | . |         |          |
+--------------------+---+----------+---------+---+---------+----------+
| 9\. Performing     |   |          |         | 1 |         |          |
| Organization Name  |   |          |         | 0 |         |          |
| and Address        |   |          |         | \ |         |          |
|                    |   |          |         | . |         |          |
| Booz Allen         |   |          |         | W |         |          |
| Hamilton Inc.,     |   |          |         | o |         |          |
| McLean, VA         |   |          |         | r |         |          |
|                    |   |          |         | k |         |          |
| Fleet Tire         |   |          |         | U |         |          |
| Consulting,        |   |          |         | n |         |          |
| Rochester Hills,   |   |          |         | i |         |          |
| MI                 |   |          |         | t |         |          |
|                    |   |          |         | N |         |          |
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|                    |   |          |         | ) |         |          |
+--------------------+---+----------+---------+---+---------+----------+
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+--------------------+---+----------+---------+---+---------+----------+
| 12\. Sponsoring    |   |          |         | 1 |         |          |
| Agency Name and    |   |          |         | 3 |         |          |
| Address            |   |          |         | \ |         |          |
|                    |   |          |         | . |         |          |
| Federal Motor      |   |          |         | T |         |          |
| Carrier Safety     |   |          |         | y |         |          |
| Administration     |   |          |         | p |         |          |
| (FMCSA)            |   |          |         | e |         |          |
|                    |   |          |         | o |         |          |
| Office of Bus and  |   |          |         | f |         |          |
| Truck Standards    |   |          |         | R |         |          |
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| (MC-PSV)           |   |          |         | p |         |          |
|                    |   |          |         | o |         |          |
| 400 7^th^ Street,  |   |          |         | r |         |          |
| SW                 |   |          |         | t |         |          |
|                    |   |          |         | a |         |          |
| Washington, DC     |   |          |         | n |         |          |
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+--------------------+---+----------+---------+---+---------+----------+
|                    |   |          |         | 1 |         |          |
|                    |   |          |         | 4 |         |          |
|                    |   |          |         | \ |         |          |
|                    |   |          |         | . |         |          |
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+--------------------+---+----------+---------+---+---------+----------+
| 15\. Supplementary |   |          |         |   |         |          |
| Notes              |   |          |         |   |         |          |
|                    |   |          |         |   |         |          |
| Contracting        |   |          |         |   |         |          |
| Officer's          |   |          |         |   |         |          |
| Technical          |   |          |         |   |         |          |
| Representative:    |   |          |         |   |         |          |
| Deborah M. Freund  |   |          |         |   |         |          |
+--------------------+---+----------+---------+---+---------+----------+
| 16\. Abstract      |   |          |         |   |         |          |
|                    |   |          |         |   |         |          |
| The overall        |   |          |         |   |         |          |
| objective of this  |   |          |         |   |         |          |
| research is to     |   |          |         |   |         |          |
| document the       |   |          |         |   |         |          |
| performance and    |   |          |         |   |         |          |
| operational        |   |          |         |   |         |          |
| characteristics of |   |          |         |   |         |          |
| leading-edge       |   |          |         |   |         |          |
| technological      |   |          |         |   |         |          |
| approaches for     |   |          |         |   |         |          |
| monitoring and     |   |          |         |   |         |          |
| maintaining        |   |          |         |   |         |          |
| commercial vehicle |   |          |         |   |         |          |
| tire pressures.    |   |          |         |   |         |          |
| Previous work      |   |          |         |   |         |          |
| sponsored by the   |   |          |         |   |         |          |
| Federal Motor      |   |          |         |   |         |          |
| Carrier Safety     |   |          |         |   |         |          |
| Administration     |   |          |         |   |         |          |
| (FMCSA) has        |   |          |         |   |         |          |
| documented the     |   |          |         |   |         |          |
| effects of         |   |          |         |   |         |          |
| improper tire      |   |          |         |   |         |          |
| inflation on both  |   |          |         |   |         |          |
| safety and direct  |   |          |         |   |         |          |
| operating costs.   |   |          |         |   |         |          |
| Improper tire      |   |          |         |   |         |          |
| inflation leads to |   |          |         |   |         |          |
| accelerated tire   |   |          |         |   |         |          |
| wear (which        |   |          |         |   |         |          |
| subsequently leads |   |          |         |   |         |          |
| to compromised     |   |          |         |   |         |          |
| braking, poor      |   |          |         |   |         |          |
| handling, and      |   |          |         |   |         |          |
| reduced            |   |          |         |   |         |          |
| stability),        |   |          |         |   |         |          |
| increased fuel     |   |          |         |   |         |          |
| consumption,       |   |          |         |   |         |          |
| increased          |   |          |         |   |         |          |
| propensity for     |   |          |         |   |         |          |
| catastrophic tire  |   |          |         |   |         |          |
| failures           |   |          |         |   |         |          |
| (blowouts),        |   |          |         |   |         |          |
| increased          |   |          |         |   |         |          |
| dangerous roadside |   |          |         |   |         |          |
| debris, and        |   |          |         |   |         |          |
| increased road     |   |          |         |   |         |          |
| calls to repair    |   |          |         |   |         |          |
| deflated tires. In |   |          |         |   |         |          |
| addition, FMCSA's  |   |          |         |   |         |          |
| research has shown |   |          |         |   |         |          |
| that despite these |   |          |         |   |         |          |
| well-understood    |   |          |         |   |         |          |
| consequences, many |   |          |         |   |         |          |
| fleets do not      |   |          |         |   |         |          |
| practice or        |   |          |         |   |         |          |
| enforce adequate   |   |          |         |   |         |          |
| tire maintenance   |   |          |         |   |         |          |
| practices---mostly |   |          |         |   |         |          |
| because checking   |   |          |         |   |         |          |
| and maintaining    |   |          |         |   |         |          |
| proper inflation   |   |          |         |   |         |          |
| is a               |   |          |         |   |         |          |
| time-consuming,    |   |          |         |   |         |          |
| inconvenient       |   |          |         |   |         |          |
| chore. As a        |   |          |         |   |         |          |
| result, fleet      |   |          |         |   |         |          |
| operators are      |   |          |         |   |         |          |
| often unaware of   |   |          |         |   |         |          |
| tire pressure      |   |          |         |   |         |          |
| issues with their  |   |          |         |   |         |          |
| vehicles.          |   |          |         |   |         |          |
|                    |   |          |         |   |         |          |
| Tire pressure      |   |          |         |   |         |          |
| monitoring and     |   |          |         |   |         |          |
| inflation systems  |   |          |         |   |         |          |
| provide a means    |   |          |         |   |         |          |
| for greatly        |   |          |         |   |         |          |
| simplifying the    |   |          |         |   |         |          |
| task of checking   |   |          |         |   |         |          |
| and maintaining    |   |          |         |   |         |          |
| tire pressure.     |   |          |         |   |         |          |
| However, there is  |   |          |         |   |         |          |
| significant        |   |          |         |   |         |          |
| product diversity  |   |          |         |   |         |          |
| in the marketplace |   |          |         |   |         |          |
| in terms of tire   |   |          |         |   |         |          |
| inflation and      |   |          |         |   |         |          |
| monitoring system  |   |          |         |   |         |          |
| design and         |   |          |         |   |         |          |
| technological      |   |          |         |   |         |          |
| approach. Further, |   |          |         |   |         |          |
| the performance,   |   |          |         |   |         |          |
| accuracy, and      |   |          |         |   |         |          |
| overall adequacy   |   |          |         |   |         |          |
| of these systems   |   |          |         |   |         |          |
| has not been well  |   |          |         |   |         |          |
| documented in a    |   |          |         |   |         |          |
| controlled and     |   |          |         |   |         |          |
| systematic         |   |          |         |   |         |          |
| fashion.           |   |          |         |   |         |          |
|                    |   |          |         |   |         |          |
| This study focuses |   |          |         |   |         |          |
| on testing and     |   |          |         |   |         |          |
| documenting the    |   |          |         |   |         |          |
| overall            |   |          |         |   |         |          |
| performance of a   |   |          |         |   |         |          |
| representative     |   |          |         |   |         |          |
| sample of          |   |          |         |   |         |          |
| commercial tire    |   |          |         |   |         |          |
| inflation and      |   |          |         |   |         |          |
| monitoring         |   |          |         |   |         |          |
| products. The      |   |          |         |   |         |          |
| study presents a   |   |          |         |   |         |          |
| technical          |   |          |         |   |         |          |
| examination of the |   |          |         |   |         |          |
| accuracy,          |   |          |         |   |         |          |
| responsiveness,    |   |          |         |   |         |          |
| resolution, and    |   |          |         |   |         |          |
| reliability of the |   |          |         |   |         |          |
| various tire       |   |          |         |   |         |          |
| pressure inflation |   |          |         |   |         |          |
| and monitoring     |   |          |         |   |         |          |
| systems. This      |   |          |         |   |         |          |
| knowledge should   |   |          |         |   |         |          |
| prove useful to    |   |          |         |   |         |          |
| fleet operators in |   |          |         |   |         |          |
| evaluating the     |   |          |         |   |         |          |
| capabilities and   |   |          |         |   |         |          |
| limitations of     |   |          |         |   |         |          |
| alternative        |   |          |         |   |         |          |
| approaches to tire |   |          |         |   |         |          |
| pressure           |   |          |         |   |         |          |
| monitoring and     |   |          |         |   |         |          |
| maintenance, and   |   |          |         |   |         |          |
| may be helpful in  |   |          |         |   |         |          |
| determining        |   |          |         |   |         |          |
| specifications for |   |          |         |   |         |          |
| future truck       |   |          |         |   |         |          |
| purchases. The     |   |          |         |   |         |          |
| information should |   |          |         |   |         |          |
| also be useful to  |   |          |         |   |         |          |
| tire pressure      |   |          |         |   |         |          |
| maintenance and    |   |          |         |   |         |          |
| monitoring system  |   |          |         |   |         |          |
| suppliers and      |   |          |         |   |         |          |
| commercial vehicle |   |          |         |   |         |          |
| manufacturers that |   |          |         |   |         |          |
| are developing new |   |          |         |   |         |          |
| tire pressure      |   |          |         |   |         |          |
| monitoring         |   |          |         |   |         |          |
| systems. To this   |   |          |         |   |         |          |
| extent, the        |   |          |         |   |         |          |
| objectives for the |   |          |         |   |         |          |
| study include      |   |          |         |   |         |          |
| providing          |   |          |         |   |         |          |
| fundamental        |   |          |         |   |         |          |
| research results   |   |          |         |   |         |          |
| to industry        |   |          |         |   |         |          |
| stakeholders       |   |          |         |   |         |          |
| concerning various |   |          |         |   |         |          |
| means of           |   |          |         |   |         |          |
| monitoring tire    |   |          |         |   |         |          |
| pressure.          |   |          |         |   |         |          |
+--------------------+---+----------+---------+---+---------+----------+
| 17\. Key Word      |   |          | 18\.    |   |         |          |
|                    |   |          | Distr   |   |         |          |
| Central Inflation  |   |          | ibution |   |         |          |
| Systems, Dual Tire |   |          | St      |   |         |          |
| Equalizers, Tire   |   |          | atement |   |         |          |
| Pressure           |   |          |         |   |         |          |
| Monitoring Systems |   |          | No      |   |         |          |
|                    |   |          | restr   |   |         |          |
|                    |   |          | ictions |   |         |          |
+--------------------+---+----------+---------+---+---------+----------+
| 19\. Security      |   | 20\.     |         |   | 21\.    | 22\.     |
| Classif. (of this  |   | Security |         |   | No. of  | Price    |
| report)            |   | Classif. |         |   | Pages   |          |
|                    |   | (of this |         |   |         |          |
| Unclassified       |   | page)    |         |   | 132     |          |
|                    |   |          |         |   |         |          |
|                    |   | Uncl     |         |   |         |          |
|                    |   | assified |         |   |         |          |
+--------------------+---+----------+---------+---+---------+----------+

<table style="width:100%;">
<colgroup>
<col style="width: 6%" />
<col style="width: 13%" />
<col style="width: 10%" />
<col style="width: 13%" />
<col style="width: 6%" />
<col style="width: 7%" />
<col style="width: 0%" />
<col style="width: 11%" />
<col style="width: 1%" />
<col style="width: 9%" />
<col style="width: 3%" />
<col style="width: 10%" />
<col style="width: 0%" />
<col style="width: 6%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="14"><strong>SI* (Modern Metric) Conversion
Factors</strong></td>
</tr>
<tr class="even">
<td colspan="5"><span class="smallcaps">Approximate Conversions to SI
Units</span></td>
<td colspan="9"><span class="smallcaps">Approximate Conversions from SI
Units</span></td>
</tr>
<tr class="odd">
<td>Symbol</td>
<td>When You Know</td>
<td>Multiply By</td>
<td>To Find</td>
<td>Symbol</td>
<td>Symbol</td>
<td colspan="3">When You Know</td>
<td>Multiply By</td>
<td colspan="2">To Find</td>
<td colspan="2">Symbol</td>
</tr>
<tr class="even">
<td colspan="5">LENGTH</td>
<td colspan="9">LENGTH</td>
</tr>
<tr class="odd">
<td>in</td>
<td>inches</td>
<td>25.4</td>
<td>millimeters</td>
<td>mm</td>
<td>mm</td>
<td colspan="3">millimeters</td>
<td>0.039</td>
<td colspan="2">inches</td>
<td colspan="2">in</td>
</tr>
<tr class="even">
<td>ft</td>
<td>feet</td>
<td>0.305</td>
<td>meters</td>
<td>m</td>
<td>m</td>
<td colspan="3">meters</td>
<td>3.28</td>
<td colspan="2">feet</td>
<td colspan="2">ft</td>
</tr>
<tr class="odd">
<td>yd</td>
<td>yards</td>
<td>0.914</td>
<td>meters</td>
<td>m</td>
<td>m</td>
<td colspan="3">meters</td>
<td>1.09</td>
<td colspan="2">Yards</td>
<td colspan="2">yd</td>
</tr>
<tr class="even">
<td>mi</td>
<td>miles</td>
<td>1.61</td>
<td>kilometers</td>
<td>km</td>
<td>km</td>
<td colspan="3">kilometers</td>
<td>0.621</td>
<td colspan="2">miles</td>
<td colspan="2">mi</td>
</tr>
<tr class="odd">
<td colspan="5">AREA</td>
<td colspan="9">AREA</td>
</tr>
<tr class="even">
<td>in<sup>2</sup></td>
<td>square inches</td>
<td>645.2</td>
<td>square millimeters</td>
<td>mm<sup>2</sup></td>
<td>mm<sup>2</sup></td>
<td colspan="3">square millimeters</td>
<td>0.0016</td>
<td colspan="2">square inches</td>
<td colspan="2">in<sup>2</sup></td>
</tr>
<tr class="odd">
<td>ft<sup>2</sup></td>
<td>square feet</td>
<td>0.093</td>
<td>square meters</td>
<td>m<sup>2</sup></td>
<td>m<sup>2</sup></td>
<td colspan="3">square meters</td>
<td>10.764</td>
<td colspan="2">square feet</td>
<td colspan="2">ft<sup>2</sup></td>
</tr>
<tr class="even">
<td>yd<sup>2</sup></td>
<td>square yards</td>
<td>0.836</td>
<td>square meters</td>
<td>m<sup>2</sup></td>
<td>m<sup>2</sup></td>
<td colspan="3">square meters</td>
<td>1.195</td>
<td colspan="2">square yards</td>
<td colspan="2">yd<sup>2</sup></td>
</tr>
<tr class="odd">
<td>ac</td>
<td>acres</td>
<td>0.405</td>
<td>hectares</td>
<td>ha</td>
<td>ha</td>
<td colspan="3">hectares</td>
<td>2.47</td>
<td colspan="2">acres</td>
<td colspan="2">ac</td>
</tr>
<tr class="even">
<td>mi<sup>2</sup></td>
<td>square miles</td>
<td>2.59</td>
<td>square kilometers</td>
<td>km<sup>2</sup></td>
<td>km<sup>2</sup></td>
<td colspan="3">square kilometers</td>
<td>0.386</td>
<td colspan="2">square miles</td>
<td colspan="2">mi<sup>2</sup></td>
</tr>
<tr class="odd">
<td colspan="5">VOLUME</td>
<td colspan="9">VOLUME</td>
</tr>
<tr class="even">
<td>fl oz</td>
<td>fluid ounces</td>
<td>29.57</td>
<td>milliliters</td>
<td>ml</td>
<td>ml</td>
<td colspan="3">milliliters</td>
<td>0.034</td>
<td colspan="2">fluid ounces</td>
<td colspan="2">fl oz</td>
</tr>
<tr class="odd">
<td>gal</td>
<td>gallons</td>
<td>3.785</td>
<td>liters</td>
<td>l</td>
<td>l</td>
<td colspan="3">liters</td>
<td>0.264</td>
<td colspan="2">gallons</td>
<td colspan="2">gal</td>
</tr>
<tr class="even">
<td>ft<sup>3</sup></td>
<td>cubic feet</td>
<td>0.028</td>
<td>cubic meters</td>
<td>m<sup>3</sup></td>
<td>m<sup>3</sup></td>
<td colspan="3">cubic meters</td>
<td>35.71</td>
<td colspan="2">cubic feet</td>
<td colspan="2">ft<sup>3</sup></td>
</tr>
<tr class="odd">
<td>yd<sup>3</sup></td>
<td>cubic yards</td>
<td>0.765</td>
<td>cubic meters</td>
<td>m<sup>3</sup></td>
<td>m<sup>3</sup></td>
<td colspan="3">cubic meters</td>
<td>1.307</td>
<td colspan="2">cubic yards</td>
<td colspan="2">yd<sup>3</sup></td>
</tr>
<tr class="even">
<td colspan="5">MASS</td>
<td colspan="9">MASS</td>
</tr>
<tr class="odd">
<td>oz</td>
<td>ounces</td>
<td>28.35</td>
<td>grams</td>
<td>g</td>
<td>g</td>
<td colspan="3">grams</td>
<td>0.035</td>
<td colspan="2">ounces</td>
<td colspan="2">oz</td>
</tr>
<tr class="even">
<td>lb</td>
<td>pounds</td>
<td>0.454</td>
<td>kilograms</td>
<td>kg</td>
<td>kg</td>
<td colspan="3">kilograms</td>
<td>2.202</td>
<td colspan="2">pounds</td>
<td colspan="2">lb</td>
</tr>
<tr class="odd">
<td>T</td>
<td>short tons (2000 lbs)</td>
<td>0.907</td>
<td>megagrams</td>
<td>Mg</td>
<td>Mg</td>
<td colspan="3">megagrams</td>
<td>1.103</td>
<td colspan="2">short tons (2000 lbs)</td>
<td colspan="2">T</td>
</tr>
<tr class="even">
<td colspan="5">TEMPERATURE (exact)</td>
<td colspan="9">TEMPERATURE (exact)</td>
</tr>
<tr class="odd">
<td>°F</td>
<td>Fahrenheit</td>
<td>5(F-32)/9</td>
<td>Celsius</td>
<td>°C</td>
<td>°C</td>
<td colspan="2">Celsius</td>
<td colspan="3">1.8 C + 32</td>
<td>Fahrenheit</td>
<td colspan="2">°F</td>
</tr>
<tr class="even">
<td></td>
<td>temperature</td>
<td>or (F-32)/1.8</td>
<td>temperature</td>
<td></td>
<td></td>
<td colspan="2">temperature</td>
<td colspan="3"></td>
<td>temperature</td>
<td colspan="2"></td>
</tr>
<tr class="odd">
<td colspan="5">ILLUMINATION</td>
<td colspan="9">ILLUMINATION</td>
</tr>
<tr class="even">
<td>fc</td>
<td>foot-candles</td>
<td>10.76</td>
<td>lux</td>
<td>lx</td>
<td>lx</td>
<td colspan="2">lux</td>
<td colspan="3">0.0929</td>
<td>foot-candles</td>
<td colspan="2">fc</td>
</tr>
<tr class="odd">
<td>fl</td>
<td>foot-Lamberts</td>
<td>3.426</td>
<td>candela/m2</td>
<td>cd/m2</td>
<td>cd/m2</td>
<td colspan="2">candela/m2</td>
<td colspan="3">0.2919</td>
<td>foot-Lamberts</td>
<td colspan="2">fl</td>
</tr>
<tr class="even">
<td colspan="5">FORCE and PRESSURE or STRESS</td>
<td colspan="9">FORCE and PRESSURE or STRESS</td>
</tr>
<tr class="odd">
<td>lbf</td>
<td>pound-force</td>
<td>4.45</td>
<td>newtons</td>
<td>N</td>
<td colspan="2">N</td>
<td>newtons</td>
<td colspan="3">0.225</td>
<td colspan="2">pound-force</td>
<td>lbf</td>
</tr>
<tr class="even">
<td>psi</td>
<td><p>pound-force</p>
<p>per square inch</p></td>
<td>6.89</td>
<td>kilopascals</td>
<td>kPa</td>
<td colspan="2">kPa</td>
<td>kilopascals</td>
<td colspan="3">0.145</td>
<td colspan="2"><p>pound-force</p>
<p>per square inch</p></td>
<td>psi</td>
</tr>
</tbody>
</table>

\* SI is the symbol for the International System of Units. Appropriate
rounding should be made to comply with Section 4 of ASTM E380.

Table of Contents

**LIST OF EXHIBITS [3](#LOE)**

**ABSTRACT [6](#Abstract)**

**EXECUTIVE SUMMARY ES-[1](#Executive_Summary)**

**Chapter 1.** **INTRODUCTION [1](#introduction)**

1.1 Background on the CV Sensor Study Program
[1](#background-on-the-cv-sensor-study-program)

1.2 Background and Rationale for This Research Effort
[2](#background-and-rationale-for-this-research-effort)

1.3 Current State of Tire Pressure Technology Development
[2](#current-state-of-tire-pressure-technology-development)

1.3.1 Dual Tire Pressure Equalizers [3](#dual-tire-pressure-equalizers)

1.3.2 Tire Pressure Monitoring Systems
[4](#tire-pressure-monitoring-systems)

1.3.3 Tire Pressure Maintenance Systems
[4](#tire-pressure-maintenance-systems)

1.3.4 Other Systems and Technologies
[6](#other-systems-and-technologies)

1.4 Research Objectives [6](#research-objectives)

1.4.1 Dual Tire Pressure Equalizers
[6](#dual-tire-pressure-equalizers-1)

1.4.2 Tire Pressure Monitoring Systems
[7](#tire-pressure-monitoring-systems-1)

1.4.3 Tire Pressure Maintenance Systems
[7](#tire-pressure-maintenance-systems-1)

1.5 Overview of Experimental Approach
[8](#overview-of-experimental-approach)

Chapter 2. DESCRIPTION OF Tested Systems
[9](#description-of-tested-systems)

2.1 Dual Tire Equalizers [10](#dual-tire-equalizers)

2.2 Tire Pressure Monitors [12](#tire-pressure-monitors)

2.3 Automatic Inflation Systems [16](#automatic-inflation-systems)

Chapter 3. TEST HARDWARE AND SETUP [19](#test-hardware-and-setup)

3.1 Test Platforms [19](#test-platforms)

3.2 Test Instrumentation Installation
[20](#test-instrumentation-installation)

3.2.1 Thermocouples [21](#thermocouples)

3.2.2 Tire Pressure Transducers [22](#tire-pressure-transducers)

3.2.3 Custom Dual-Flow Rotary Union and Slip Ring Assemblies
[23](#custom-dual-flow-rotary-union-and-slip-ring-assemblies)

3.2.4 Custom Pressure Control Manifold
[24](#custom-pressure-control-manifold)

3.2.5 Brake Reservoir and Treadle Valve Pressure Transducers
[26](#brake-reservoir-and-treadle-valve-pressure-transducers)

3.2.6 Digital Marker Switch [26](#digital-marker-switch)

3.2.7 Non-Contact Fifth Wheel [27](#non-contact-fifth-wheel)

3.2.8 DAS..... [27](#das)

Chapter 4. TEST PLAN [30](#test-plan)

4.1 Test Matrix [30](#test-matrix)

4.1.1 Functionality Test (Static and Dynamic)
[31](#functionality-test-static-and-dynamic)

4.1.2 Threshold Warning Level Test [31](#threshold-warning-level-test)

4.1.3 Loaded Test at High Speed [31](#loaded-test-at-high-speed)

4.1.4 Failure Modes Test [31](#failure-modes-test)

4.1.5 Disablement Test [32](#disablement-test)

4.1.6 Operator Interface Evaluation [32](#operator-interface-evaluation)

4.1.7 Gate Reader Evaluation [32](#gate-reader-evaluation)

4.2 Data Collection Process [32](#data-collection-process)

Chapter 5. TEST RESULTS [33](#test-results)

5.1 Dual Tire Equalizers [33](#dual-tire-equalizers-1)

5.1.1 Static and Dynamic Functionality Tests
[34](#static-and-dynamic-functionality-tests)

5.1.2 Threshold Warning Tests [40](#threshold-warning-tests)

5.1.3 Failure Modes Tests [43](#failure-modes-tests)

5.1.4 Disablement Tests [46](#disablement-tests)

5.1.5 Operator Interface Evaluation
[47](#operator-interface-evaluation-1)

5.2 Tire Pressure Monitoring Systems
[48](#tire-pressure-monitoring-systems-2)

5.2.1 Functionality Test [49](#functionality-test)

5.2.2 Threshold Warning Level Test [54](#threshold-warning-level-test-1)

5.2.3 Loaded Test at High Speed [57](#loaded-test-at-high-speed-1)

5.2.4 Disablement Test [64](#disablement-test-1)

5.2.5 Operator Interface Evaluation
[67](#operator-interface-evaluation-2)

5.2.6 Gate Reader Evaluation [71](#gate-reader-evaluation-1)

5.3 Central Inflation Systems [72](#central-inflation-systems)

5.3.1 Functionality Tests [73](#functionality-tests)

5.3.2 Threshold Warning Level Tests [80](#threshold-warning-level-tests)

5.3.3 Loaded Test at High Speed [83](#loaded-test-at-high-speed-2)

5.3.4 Failure Modes Test [86](#failure-modes-test-1)

5.3.5 Disablement Test [89](#disablement-test-2)

5.3.6 Operator Interface Evaluation
[93](#operator-interface-evaluation-3)

Chapter 6. OBSERVATIONS AND CONCLUSIONS
[95](#observations-and-conclusions)

6.1 Dual Tire Equalizers [95](#dual-tire-equalizers-2)

6.2 Tire Pressure Monitoring Systems
[95](#tire-pressure-monitoring-systems-3)

6.3 Central Inflation Systems [97](#central-inflation-systems-cis)

6.4 General System Performance and Test Observations
[98](#general-system-performance-and-test-observations)

6.5 Recommended Future Research [99](#recommended-future-research)

**APPENDIX A -- TPMS, EQUALIZERS, AND INFLATION SYSTEMS
[104](#Appendix)**

[]{#LOE .anchor}List of Exhibits

[Exhibit 1.1 -- Dual Tire Equalizer Diagram
3](#__RefHeading___Toc149980535)

[Exhibit 1.2 -- Example Wheel-Mounted Tire Pressure Monitoring System
4](#__RefHeading___Toc149980536)

[Exhibit 1.3 -- Rotary Union Style CIS 5](#__RefHeading___Toc149980537)

[Exhibit 1.4 -- Hollow Axle Style CIS 5](#__RefHeading___Toc149980538)

[Exhibit 2.1 -- Selected Systems for Testing
9](#__RefHeading___Toc149980539)

[Exhibit 2.2 -- Link Cat's Eye TPMS Dual-Tire Equalizer
11](#__RefHeading___Toc149980540)

[Exhibit 2.3 -- V-Tech Tire-Knight-S Dual-Tire Equalizer
11](#__RefHeading___Toc149980541)

[Exhibit 2.4 -- Advantage PressurePro TPMS
13](#__RefHeading___Toc149980542)

[Exhibit 2.5 -- WABCO Integrated Vehicle Tire Pressure Monitoring TPMS
14](#__RefHeading___Toc149980543)

[Exhibit 2.6 -- HCI Tire-SafeGuard TPMS
14](#__RefHeading___Toc149980544)

[Exhibit 2.7 -- SmarTire TPMS 15](#__RefHeading___Toc149980545)

[Exhibit 2.8 -- Michelin eTire TPMS 16](#__RefHeading___Toc149980546)

[Exhibit 2.9 -- Arvin Meritor PSI Tire Inflation System
17](#__RefHeading___Toc149980547)

[Exhibit 2.10 -- Gio-Set Vigia Automatic Tire Pressure System
18](#__RefHeading___Toc149980548)

[Exhibit 3.1 ‑ Tractor/Trailer Test Platform
19](#__RefHeading___Toc149980549)

[Exhibit 3.2 -- Tractor/Trailer Specification
19](#__RefHeading___Toc149980550)

[Exhibit 3.3 -- Motorcoach Test Platform
20](#__RefHeading___Toc149980551)

[Exhibit 3.4 -- Motorcoach Specification
20](#__RefHeading___Toc149980552)

[Exhibit 3.5 -- Instrumentation Locations
21](#__RefHeading___Toc149980553)

[Exhibit 3.6 -- Tire Temperature Thermocouples and Pressure Lines
22](#__RefHeading___Toc149980554)

[Exhibit 3.7 -- Pressure Transducer 23](#__RefHeading___Toc149980555)

[Exhibit 3.8 -- Dual-Flow Rotary Union and Slip Ring Assembly
24](#__RefHeading___Toc149980556)

[Exhibit 3.9 -- Pressure Control Manifold Schematic
25](#__RefHeading___Toc149980557)

[Exhibit 3.10 -- Pressure Control Manifold and Metering Valve
26](#__RefHeading___Toc149980558)

[Exhibit 3.11 -- Digital Marker Switch Photo
27](#__RefHeading___Toc149980559)

[Exhibit 3.12 - Link DAS 28](#__RefHeading___Toc149980560)

[Exhibit 3.13 ‑ Links DAS Specification
28](#__RefHeading___Toc149980561)

[Exhibit 3.14 -- Sensor Channels 29](#__RefHeading___Toc149980562)

[Exhibit 4.1 -- Test Matrix 31](#__RefHeading___Toc149980563)

[Exhibit 5.1 -- Dual Tire Equalizer Functionality Test Procedures
34](#__RefHeading___Toc149980564)

[Exhibit 5.2 -- Link Equalizer Static Equalizer Functionality Test LFID
75 psi 35](#__RefHeading___Toc149980565)

[Exhibit 5.3 -- Link Equalizer Static Equalizer Functionality Test LFID
55 psi 36](#__RefHeading___Toc149980566)

[Exhibit 5.4 -- Link Equalizer Static Functionality Test Data
36](#__RefHeading___Toc149980567)

[Exhibit 5.5 -- V-Tech Equalizer Static Functionality Test Data
37](#__RefHeading___Toc149980568)

[Exhibit 5.6 -- V-Tech Equalizer Dynamic Equalizer Functionality Test
LFID 85 psi 38](#__RefHeading___Toc149980569)

[Exhibit 5.7 -- V-Tech Equalizer Dynamic Equalizer Functionality Test
LFID 55 psi 39](#__RefHeading___Toc149980570)

[Exhibit 5.8 -- Link Equalizer Dynamic Functionality Test Data
39](#__RefHeading___Toc149980571)

[Exhibit 5.9 -- V-Tech Equalizer Dynamic Functionality Test Data
40](#__RefHeading___Toc149980572)

[Exhibit 5.10 -- Dual Tire Equalizer Threshold Warning Test Procedures
40](#__RefHeading___Toc149980573)

[Exhibit 5.11 -- Link Equalizer Static Slow Leak Test
41](#__RefHeading___Toc149980574)

[Exhibit 5.12 -- Link Equalizer Dynamic Slow Leak Test
42](#__RefHeading___Toc149980575)

[Exhibit 5.13 -- Link Equalizer Threshold Warning Test Data
42](#__RefHeading___Toc149980576)

[Exhibit 5.14 -- V-Tech Equalizer Threshold Warning Test Data
43](#__RefHeading___Toc149980577)

[Exhibit 5.15 -- Dual Tire Equalizer Failure Modes Test Procedures
43](#__RefHeading___Toc149980578)

[Exhibit 5.16 -- V-Tech Equalizer Static Rapid Leak LFID Test
44](#__RefHeading___Toc149980579)

[Exhibit 5.17 -- V-Tech Equalizer Dynamic Rapid Leak LFID Test
45](#__RefHeading___Toc149980580)

[Exhibit 5.18 -- Link Equalizer Failure Mode Test Data
45](#__RefHeading___Toc149980581)

[Exhibit 5.19 -- V-Tech Equalizer Failure Mode Test Data
46](#__RefHeading___Toc149980582)

[Exhibit 5.20 -- Dual Tire Equalizer Failure Modes Test Procedures
46](#__RefHeading___Toc149980583)

[Exhibit 5.21 -- Dual Tire Equalizer Failure Modes Test Data
47](#__RefHeading___Toc149980584)

[Exhibit 5.22 -- Link Equalizer Pressure Gauge
48](#__RefHeading___Toc149980585)

[Exhibit 5.23 -- V-Tech Equalizer Pressure Gauge
48](#__RefHeading___Toc149980586)

[Exhibit 5.24 -- TPMS Functionality Test Procedures
49](#__RefHeading___Toc149980587)

[Exhibit 5.25 -- Static Functionality Test of Valve-Stem-Mounted TPMS
(RROD) 50](#__RefHeading___Toc149980588)

[Exhibit 5.26 -- Dynamic Functionality Test of Valve-Stem-Mounted TPMS
(RROD) 51](#__RefHeading___Toc149980589)

[Exhibit 5.27 -- Static Functionality Test of Wheel-Mounted TPMS (RROD)
52](#__RefHeading___Toc149980590)

[Exhibit 5.28 -- Dynamic Functionality Test of Wheel-Mounted TPMS (RROD)
53](#__RefHeading___Toc149980591)

[Exhibit 5.29 -- TPMS Threshold Warning Level Test Procedures
54](#__RefHeading___Toc149980592)

[Exhibit 5.30 -- Advantage PressurePro Valve-Stem-Mounted TPMS Threshold
Warning Level Test 55](#refheading___toc149980593)

[Exhibit 5.31 -- Valve-Stem-Mounted TPMS Threshold Warning Level Tests
Results 56](#__RefHeading___Toc149980594)

[Exhibit 5.32 -- Wheel-Mounted TPMS Threshold Warning Level Test
56](#__RefHeading___Toc149980595)

[Exhibit 5.33 -- Valve-Stem-Mounted TPMS Threshold Warning Level Tests
Results 57](#__RefHeading___Toc149980596)

[Exhibit 5.34 -- Example of Pressure Increase Due to Sustained
High-speed Driving 58](#__RefHeading___Toc149980597)

[Exhibit 5.35 -- TPMS Loaded Test at High-Speed Test Procedures
59](#__RefHeading___Toc149980598)

[Exhibit 5.36 -- Valve-Stem-Mounted TPMS Loaded Test at High Speed
60](#__RefHeading___Toc149980599)

[Exhibit 5.37 -- Valve-Stem-Mounted TPMS Loaded Test at High Speeds
Results 61](#__RefHeading___Toc149980600)

[Exhibit 5.38 -- Wheel-Mounted TPMS Loaded Test at High Speed
62](#__RefHeading___Toc149980601)

[Exhibit 5.39 -- Wheel-Mounted TPMS Loaded Test at High Speeds Results
63](#__RefHeading___Toc149980602)

[Exhibit 5.40 - ETire TPMS Loaded Test at High Speed
64](#__RefHeading___Toc149980603)

[Exhibit 5.41 -- ETire TPMS Loaded Test at High Speeds Results
64](#__RefHeading___Toc149980604)

[Exhibit 5.42 -- Advantage PressurePro Disablement Results
65](#__RefHeading___Toc149980605)

[Exhibit 5.43 -- IVTM Disablement Results
65](#__RefHeading___Toc149980606)

[Exhibit 5.44 -- Tire-SafeGuard Disablement Results
66](#__RefHeading___Toc149980607)

[Exhibit 5.45 -- SmarTire Disablement Results
67](#__RefHeading___Toc149980608)

[Exhibit 5.46 -- Advantage PressurePro Operator Interface
68](#__RefHeading___Toc149980609)

[Exhibit 5.47 -- IVTM Operator Interface
68](#__RefHeading___Toc149980610)

[Exhibit 5.48 -- Tire-SafeGuard Operator Interface
69](#__RefHeading___Toc149980611)

[Exhibit 5.49 -- SmarTire Operator Interface
69](#__RefHeading___Toc149980612)

[Exhibit 5.50 -- ETire Handheld Reader Interface
70](#__RefHeading___Toc149980613)

[Exhibit 5.51 -- Photo of Gate Reader Installation in Indianapolis, IN
71](#__RefHeading___Toc149980614)

[Exhibit 5.52 -- Gate Reader Evaluation Results
72](#__RefHeading___Toc149980615)

[Exhibit 5.53 -- CIS Static/Dynamic Functionality Test Procedures
73](#__RefHeading___Toc149980616)

[Exhibit 5.54 -- Vigia CIS Static Functionality Test Data
74](#__RefHeading___Toc149980617)

[Exhibit 5.55 -- Vigia CIS RTAG Static Functionality Test
75](#__RefHeading___Toc149980618)

[Exhibit 5.56 -- Vigia CIS Dynamic Functionality Test Data
76](#__RefHeading___Toc149980619)

[Exhibit 5.57 -- Vigia CIS LFOD Dynamic Functionality Test
77](#__RefHeading___Toc149980620)

[Exhibit 5.58 -- Static Functionality Test of PSI CIS
78](#__RefHeading___Toc149980621)

[Exhibit 5.59 -- Static Functionality Test Results for PSI CIS
78](#__RefHeading___Toc149980622)

[Exhibit 5.60 -- Dynamic Functionality Test of PSI CIS
79](#__RefHeading___Toc149980623)

[Exhibit 5.61 -- Dynamic Functionality Test Results for PSI CIS
79](#__RefHeading___Toc149980624)

[Exhibit 5.62 -- CIS Threshold Warning Test Procedures
80](#__RefHeading___Toc149980625)

[Exhibit 5.63 -- Vigia CIS Threshold Warning Test (45 mph) Data
80](#__RefHeading___Toc149980626)

[Exhibit 5.64 -- Vigia CIS RFS Threshold Warning Test
81](#__RefHeading___Toc149980627)

[Exhibit 5.65 -- Threshold Warning Level Test of PSI CIS
82](#__RefHeading___Toc149980628)

[Exhibit 5.66 -- Threshold Warning Test Results for PSI CIS
83](#__RefHeading___Toc149980629)

[Exhibit 5.67 -- CIS Loaded Dynamic Test at High-Speed Test Procedures
83](#__RefHeading___Toc149980630)

[Exhibit 5.68 -- Vigia CIS Loaded Test at High Speed (75 mph) Data
84](#__RefHeading___Toc149980631)

[Exhibit 5.69 -- Vigia CIS RTAG Loaded High-Speed Test with Rapid Leak
85](#__RefHeading___Toc149980632)

[Exhibit 5.70 -- Failure Modes Test Procedures
86](#__RefHeading___Toc149980633)

[Exhibit 5.71 -- Vigia CIS RFS Failure Modes Test
87](#__RefHeading___Toc149980634)

[Exhibit 5.72 -- Vigia CIS Failure Modes Test Total System Air Loss
88](#__RefHeading___Toc149980635)

[Exhibit 5.73 -- Failure Modes Test of PSI CIS
89](#__RefHeading___Toc149980636)

[Exhibit 5.74 -- CIS Disablement Modes Test Procedures
90](#__RefHeading___Toc149980637)

[Exhibit 5.75 -- Vigia CIS Disablement Mode 1 Test Inflation System #2
91](#__RefHeading___Toc149980638)

[Exhibit 5.76 -- Vigia CIS Disablement Mode 1 Test System Console and
Instrument Panel 91](#__RefHeading___Toc149980639)

[Exhibit 5.77 -- Vigia CIS Disablement Mode 4 Rotor Feed Hose Cut
92](#__RefHeading___Toc149980640)

[Exhibit 5.78 -- Vigia CIS Disablement Mode Test Results
93](#__RefHeading___Toc149980641)

[Exhibit 5.79 -- PSI CIS Disablement Results
93](#__RefHeading___Toc149980642)

[Exhibit 5.80 -- Vigia CIS Operator Interface
94](#__RefHeading___Toc149980643)

[Exhibit 5.81 -- Warning Indicator for the PSI CIS
94](#__RefHeading___Toc149980644)

[]{#Abstract .anchor}ABSTRACT

The overall objective of this research is to document the performance
and operational characteristics of leading-edge technological approaches
for monitoring and maintaining commercial vehicle tire pressures.
Previous work sponsored by the Federal Motor Carrier Safety
Administration (FMCSA) has documented the effects of improper tire
inflation on both safety and direct operating costs. Improper tire
inflation leads to accelerated tire wear (which subsequently leads to
compromised braking, poor handling, and reduced stability), increased
fuel consumption, increased propensity for catastrophic tire failures
(blowouts), increased dangerous roadside debris, and increased road
calls to repair deflated tires. In addition, FMCSA's research has shown
that despite these well-understood consequences, many fleets do not
practice or enforce adequate tire maintenance practices---mostly because
checking and maintaining proper inflation is a time-consuming,
inconvenient chore. As a result, fleet operators are often unaware of
tire pressure issues with their vehicles.

Tire pressure monitoring and inflation systems provide a means for
greatly simplifying the task of checking and maintaining tire pressure.
However, there is significant product diversity in the marketplace in
terms of tire inflation and monitoring system design and technological
approach. Further, the performance, accuracy, and overall adequacy of
these systems have not been well documented in a controlled and
systematic fashion.

This study focuses on testing and documenting the overall performance of
a representative sample of commercial tire inflation and monitoring
products. The study presents a technical examination of the accuracy,
responsiveness, resolution, and reliability of the various tire pressure
inflation and monitoring systems. This knowledge should prove useful to
fleet operators in evaluating the capabilities and limitations of
alternative approaches to tire pressure monitoring and maintenance, and
may be helpful in determining specifications for future truck purchases.
The information should also be useful to tire pressure maintenance and
monitoring system suppliers and commercial vehicle manufacturers that
are developing new tire pressure monitoring systems. To this extent,
this study's objectives include providing fundamental research results
to industry stakeholders concerning various means of monitoring tire
pressure.

[]{#Executive_Summary .anchor}EXECUTIVE SUMMARY

**Project Funding**

Under Section 5117 of the Transportation Equity Act for the 21^st^
Century of 1998 (TEA-21), Congress required the U.S. Department of
Transportation (USDOT) to "conduct research on the deployment of a
system of advanced sensors and signal processors in trucks and tractor
trailers to determine axle and wheel alignment, monitor collision alarm,
check tire pressure and tire balance conditions, measure and detect load
distribution in the vehicle, and adjust automatic braking systems." The
research program responding to this directive is called the Commercial
Vehicle Safety Technology Diagnostics and Performance Enhancement
Program (CV Sensor Study Program).

This study was completed as a task under the CV Sensor Study Program.

Background and Rationale

Early research work sponsored by the Federal Motor Carrier Safety
Administration ( FMCSA) indicates that a significant portion of fleet
operators do not regularly perform tire pressure maintenance to the
standards recommended by tire manufacturers.[^1] For example, FMCSA
research has shown that:

-   Approximately 7 percent of all tires are under-inflated by 20 psi or
    more. Only 44 percent (approximately) of all tires are within ±5 psi
    of their target pressure.

-   Tire-related costs are the single largest maintenance cost item for
    commercial vehicle fleet operators. National average tire-related
    costs per tractor-trailer are about 2 cents per mile, or about
    \$2,500 for an annual 125,000-mile operation.

-   For the average fleet operator in the United States, improper tire
    inflation increases the annual procurement costs for both new and
    retreaded tires by about 10 to 13 percent.

-   Improper tire inflation reduces fuel economy by about 0.6 percent.

-   Improper tire inflation is likely responsible for about one road
    call per year per tractor-trailer combination due to weakened and
    worn tires.

-   Improper inflation increases total tire-related costs by
    approximately \$600 to \$800 annually per tractor-trailer
    combination.

Commercial vehicle tire inflation and condition directly link to
stopping distance and handling, and thus overall safety. Properly
maintained and performing tires aid drivers in preventing and mitigating
crash situations. Properly inflated tires could help prevent or mitigate
crashes even when the tires are not the initial cause of the crash.
Eliminating or mitigating key mechanical problems, including tire
issues, would likely yield a significant reduction in the number and
severity of injuries sustained in commercial vehicle-related crashes.

To address these issues, numerous types of tire pressure monitoring and
inflation systems have emerged in the marketplace over the last decade.
However, the market penetration of tire pressure maintenance equipment
has remained comparatively low. Tire pressure monitoring and inflation
systems provide a means for simplifying the task of checking and
maintaining tire pressure. However, there is significant product
diversity in the marketplace in terms of tire inflation and monitoring
system design and technological approach. Further, the performance,
accuracy, and overall adequacy of these systems have not been well
documented in a controlled and systematic fashion.

Study Objective

The overall objective of this research study is to document the
performance, accuracy, and operational characteristics of leading-edge
technological approaches to commercial vehicle tire pressure monitoring
and maintenance systems (TPMS). The study focuses on the ability of the
various sensors to present accurate tire pressure readings, to detect
slow and rapid changes in tire pressure, and to maintain tire pressure
under adverse conditions including partial failure of the device. The
study examines the following TPMS technology categories:

-   Dual tire equalizers to balance pressures between tires in a dual
    installation

-   Tire pressure monitors to keep track of the pressures in each tire

-   Tire pressure maintenance systems to maintain tire pressure at
    desired levels

Equipping a commercial motor vehicle (CMV) with sensors and transmitters
to accurately and reliably measure the pressure in each tire could offer
the following benefits:

-   Warn the driver and/or maintenance personnel if tire pressure drops
    to an unsafe level---and help with diagnosis of the problem

-   Provide information to enforcement personnel for use during roadside
    inspections

-   Reduce tire wear and increase service life

-   Alert the driver to a catastrophic failure of a tire, as sometimes
    there is little feedback to the driver by noise or vibration during
    operation (e.g., a trailer tire failure)

Systems that automatically (or continuously) maintain tire inflation
pressure might offer even more benefits such as increased fuel
economy---provided they had a high level of reliability, were easy to
maintain, and were considered "affordable."

Overview of Project Approach

The study team installed a variety of tire pressure monitoring and
automatic inflation systems (collectively described as tire pressure
management systems, or TPMS) on a conventional tractor-trailer
combination vehicle and on a motorcoach. The team tested both vehicles
under controlled conditions on a test track at the Transportation
Research Center (TRC) in Columbus, OH. This approach facilitated
objective, accurate comparisons of the systems, and eliminated problems
associated with the repeatability of the test procedures when comparing
different systems.

In addition, the team contacted and interviewed numerous industry
stakeholders during the study. These stakeholders included suppliers of
the various technologies examined, who assisted the team in compiling
information about the various TPMS technologies and their market
penetration. The team used this information in recommending the systems
for assessment. The stakeholders also assisted in developing the test
program and the test procedures. The companies and individuals contacted
provided information that was compiled in this report.

Summary of Results

The following are key observations and results from the testing of the
sensor technologies.

Dual Tire Equalizers

Tire pressure equalizer systems balance dual tire pressures by providing
a pathway for air to transfer between two tires in a dual installation
and also provide an indication of tire pressure. A pressure actuated
valve connected by hoses to the valve stems of the tires maintains an
open position to allow air to flow between the tires when the combined
pressure of the two tires is above a preset level (typically 90 psi).
The pressure actuated valve closes and isolates the tires during slow
leaks or instantaneous air losses after the combined pressure of the two
tires drops approximately 10 psi to prevent both tires from going flat.
A central fill valve incorporated in these devices allows both tires in
the assembly to be aired simultaneously. The use of equalizers should
improve irregular tire wear (i.e., cupping) caused by pressure
differentials between dual tires. Visual indicators are also
incorporated in the equalizers to provide the operator with a quick
indication of the tire pressure levels during the pre-trip inspection
without requiring the operator to perform a manual tire pressure check.

The team installed dual tire equalizers from two different manufacturers
on the tractor-trailer test platform. The following are some key
observations and conclusions related to dual tire equalizers:

-   Dual tire equalizers are effective in balancing the pressures
    between the two tires. The equalization technologies function as
    designed under both static and dynamic conditions.

-   Both systems prevented the total loss of pressure in one or both
    tires in every failure mode implemented.

-   The two equalization systems were effective in isolating an intact
    tire from the adjacent tire with an artificially induced major air
    loss.

-   A disablement test, where a hose was cut to simulate damage from
    road debris, produces a total loss of air from one tire in a dual
    installation, while the other tire was protected by a check valve.

-   Both equalizer systems included a visual indicator that can provide
    a gross indication of tire pressure. They provide an indication that
    the tire pressure is or is not within its target range. However, if
    the pressure falls below this range, they only show a "low" pressure
    condition and do not indicate the extent of under-inflation.

-   While the indicators provide a good visual indication of tire
    pressure, they can be difficult to read as they are mounted on the
    wheel and can become obscured by dirt.

Tire Pressure Monitoring Systems

Tire pressure monitoring systems consist of a valve stem, wheel- or
tire-mounted sensor, antennae, receiver, and display unit. The
battery-powered sensors mounted on each valve stem, wheel, or tire on
the vehicle transmit a radio frequency (RF) signal, which includes the
tire pressure data, to an antennae mounted on the vehicle. A receiver
with an integrated electronic control unit (ECU) processes the signal
transmitted to the antennae, and displays the tire pressure information
on a driver's cab-mounted display. The system also includes audible
alarms and visible warning lights.

The study team tested five different tire pressure monitoring systems
for this project. These included one tire-mounted, two
valve-stem-mounted, and two wheel-mounted tire pressure monitoring
systems. The following are some key observations and conclusions on the
TPMS technology.

**General TPMS Observations**

-   In general, each valve-, wheel-, or tire-mounted system tested
    exhibited base-level functionality as specified by the manufacturer
    of the individual systems.

-   The tire pressure monitoring systems tested were generally accurate
    to within 2 to 3 psi from the values measured by the calibrated test
    instrumentation pressure measurement transducers.

-   Low-pressure warning thresholds are "factory set" on some systems,
    but user-configurable on others. For those systems with factory
    settings, different warning levels ranging from 12 to 25 percent
    below target pressure were observed. All systems tested were
    generally within a 2- to 3-psi range of the expected warning
    threshold (whether set at the factory or by the user).

-   Many of the TPMS tested used RF communications to transmit data
    between the sensors and the display unit or ECU. The relatively long
    length of typical CMVs means that additional on-board antennas are
    required for some of the systems to receive the sensor signals from
    trailer or tag axle tires. Disconnected or damaged antennas can lead
    to signal loss from the sensors.

**Valve-Stem-Mounted TPMS Observations**

-   Typically, valve-stem-mounted tire pressure monitoring systems do
    not compensate for increases in tire pressure as a result of
    increased tire temperature from high-speed driving. However, one
    valve-stem-mounted system tested in this study did include
    temperature compensation.

-   One of the systems tested initiated a warning when the pressure fell
    below a preset value (\~20 percent below target); however, the
    warning remained active until the tire was inflated to a higher
    value (\~15 percent below target). This pressure band between the
    alarm pressure and alarm deactivation pressure prevents intermittent
    warnings to the driver.

-   Valve-stem-mounted systems are susceptible to loss because they have
    to be removed during wheel mounting and dismounting for vehicle
    maintenance and inspection. Their relative ease of removal could
    also make them susceptible to theft.

**Wheel-Mounted TPMS Observations**

-   The study team's understanding from a review of product literature
    was that wheel-mounted technology included temperature compensation,
    and typically provided the best performance in correcting for tire
    temperature. However, during the high-speed testing, both
    wheel-mounted systems tested had their active warnings disabled when
    the pressure increased in the tire as a result of increased tire
    temperature. This occurred intermittently between the various test
    runs on different axles, although the test data suggests that the
    systems were able to compensate for large increases in tire
    temperature (greater than 20 degrees F) a majority of the time, but
    smaller increases with corresponding pressure increases were not
    compensated for. This could result in increasing tire temperatures
    preventing a low-pressure warning.

-   The team discovered during the TPMS installations that the
    wheel-mounted technologies may be vulnerable to damage during tire
    mounting/demounting.

**Tire-Mounted TPMS Observations**

-   The tire-mounted technology tested included temperature
    compensation, which, when read by the handheld reader, displayed
    both the temperature-corrected pressure and the uncorrected pressure
    at ambient tire temperature.

-   The tire-mounted technology tested required the use of handheld or
    gate reader devices to inspect tires (no in-cab display was provided
    with the systems). However, the system was unique among those tested
    in that it included an Internet-based tire maintenance and tracking
    database application hosted by the system manufacturer.

-   For the tire-mounted units, the gate reader clearances were very
    tight and required very slow vehicle speeds, less than 5 mph.

Central Inflation Systems

Constant central tire inflation systems (CIS) use the air from the
vehicle's air compressor that is stored in the air brake reservoirs
(tanks) to maintain tire pressure at a desired level. The CIS are
plumbed to the vehicle's secondary reservoir that supplies air to the
front brakes. The CIS do not take air from the primary reservoir that
supplies air for the rear brakes, which are responsible for the majority
of the braking power of the CMV. These systems are either plumbed
through the axle, or externally through the use of a rotary union at the
wheel hub. They automatically sense the tire pressures and inflate the
tires when air is lost. The benefits of these systems are the
elimination of manual tire pressure checks and the ability to continue
operating the vehicle with minor air leaks in the tires.

CIS are available for all types of CMVs. In this test, one system was
tested on the motorcoach and one was tested on the trailer of a
tractor-trailer. The following are key observations and conclusions
regarding CIS.

**Central Inflation System Observations**

-   The tested CIS generally perform as designed and specified by the
    manufacturer. The systems performed well in both static and dynamic
    conditions.

-   In the testing involving leak rates, the motorcoach CIS was able to
    keep up with leak rates up to 5 to 8 psi/min. Ultimately, this
    system's performance was limited by the vehicle's air compressor
    duty cycle and the compressed air supply and storage system design.

-   The CIS tested on the trailer could maintain adequate tire pressure
    with slow leakage rates (less than 1.0 psi/min), but would not
    maintain adequate tire pressure for higher leakage rates. This
    system appeared to be limited by its rate of air flow to the tires
    more than by a limitation of the on-board compressor and air system.

-   During testing with heavy braking and simultaneous tire leaks, the
    vehicles' primary and secondary air reservoir pressures remained
    above the level required for safe brake operation. The compressor
    had no difficulty recharging the reservoirs without having to run
    continuously.

-   Both CIS tested protected the intact tires from deflating when a
    catastrophic air leak was simulated in one of the other tires in the
    system. In this regard, the systems functioned in a manner similar
    to the dual tire equalizers isolation circuits.

Summary of General System Performance and Test Observations

Observations and conclusions about brake system performance and testing
are as follows:

-   Vehicle air systems are not optimized to support a CIS with very
    high leakage rates; therefore, the functionality of the CIS is often
    limited by the vehicle's air system. Additionally, there may be some
    long-term impact to the CMV's air system when subjected to a high
    leakage rate from the secondary reservoir, which the CIS utilizes
    for its supply air. These leak rates would cause an increase in the
    duty cycle of the compressor, and would increase maintenance
    requirements and decrease compressor service life.

-   Installation time for systems vary. In general, valve-stem-mounted
    TPMS and dual tire equalizers were less time consuming to install
    (generally, several hours), followed by wheel-mounted TPMS,
    tire-mounted TPMS, and CIS that require up to a full day for
    installation.

-   Temperature compensation in TPMS requires further refinement. During
    high-speed driving, the warning indicators actuated intermittently
    on some systems as tire temperatures increased. The effect of
    increased temperature deactivating low-pressure alarms could prevent
    the system from alerting a driver to a low-pressure condition.

Recommended Future Research

This project has provided comprehensive baseline assessments of a
variety of state-of-the-practice tire pressure monitoring and inflation
systems. These assessments were performed under controlled test track
conditions. Between test sequences, the study team checked and
recalibrated the various sensors and systems as needed. In the "real
world" of CMV operations, inspection and maintenance are generally
performed at much longer intervals---for CMVs operating in interstate
commerce, the mandatory periodic inspection interval is 12 months.
Furthermore, the useful operating life of a heavy-duty truck or
motorcoach can be 10 to 12 years or longer, and the operating
environment is much more severe than on the test track. Therefore, there
is a need to subject tire pressure monitoring and maintenance sensors
and systems to the rigors of operation that a CMV would experience
during the course of revenue service.

FMCSA-sponsored field operational tests (FOT) involving the use of a
transit bus fleet and a commercial trucking fleet are currently
underway. This study should provide useful information on longer-term
utility, reliability, and maintainability.

# INTRODUCTION

This chapter provides information on the following:

-   Background on the Commercial Vehicle Safety Technology Diagnostics
    and Performance Enhancement Program (CV Sensor Study Program)

-   Background and rationale for this research project

-   Current state of tire pressure technology development

-   Research objectives

-   Overview of process approach

## Background on the CV Sensor Study Program

The purpose of the CV Sensor Study Program is to \"define performance
requirements, assess benefits, and accelerate deployment of driver and
vehicle assistance products and systems and, in particular, advanced
sensor and signal processors in trucks and tractor trailers with an
emphasis in on-board diagnostic and improved safety-related products.\"

The program involved soliciting input from key industry stakeholders
(fleet operators, manufacturers, and suppliers) on potential research
initiatives that complement (rather than duplicate) efforts by private
industry. Objectives of the research include evaluating the probable
impact of selected vehicle technologies on improving overall trucking
safety, and assessing their cost savings potential and/or operational
benefits---thus helping to create market demand and encourage
commercialization.

To help identify possible research areas, the study team completed the
following tasks:

-   An extensive literature search of relevant technical journals and
    databases

-   Individual interviews and discussions with representatives from
    truck and trailer manufacturers, fleet operators, owner operators,
    and industry suppliers, as well as staff at the National Highway
    Traffic Safety Administration (NHTSA), FMCSA, and Federal Highway
    Administration (FHWA) who are involved in commercial vehicle safety
    research

-   A meeting of key industry stakeholders to review candidate research
    areas and make suggestions regarding future work under the CV Sensor
    Study Program

As a result of this background research and interviews, the team
identified the following candidate research areas:

-   Brakes and related controls

-   Tire inflation and condition monitoring systems

-   Truck and tractor alignment ("dynamic alignment")

-   Testing and analysis of high-speed data bus networks (J1939)

-   Cost, benefits, and implementation issues

-   "Active suspensions" and other systems related to event data
    recorder suspension

-   Advanced vehicle diagnostic and prognostic tools

-   Issues related to implementation of "Smart Copilot" on-board systems

This list was meant to be a "work in process" and to direct research.
Project team members continue to monitor and assess new technologies
that could improve vehicle safety, and to engage industry in discussions
regarding the appropriateness of specific research projects.

**The focus of this research effort is on the tire inflation and
condition monitoring systems research area.**

## Background and Rationale for This Research Effort

TPMS technologies show significant promise for improving safety and
reducing costs in the commercial vehicle industry. Improving tire
pressure management directly relates to improved vehicle stability,
reduced tire wear and damage, better braking, improved fuel efficiency,
and fewer roadside breakdowns---thus enhanced safety. Overall, improving
tire pressure maintenance and general tire management can impact carrier
productivity.

FMCSA, in a prior task under the CV Sensor Study Program contract,
completed a comprehensive survey of the tire pressure maintenance
practices by fleets and owner operators. This prior study included a
market assessment of TPMS available at the time and developed high-level
cost-benefit analyses of TPMS based on preliminary estimates of the
systems' effectiveness for improving the tire maintenance practice of
various type of fleets. This previous research work indicates that a
significant portion of motor carriers and other commercial vehicle fleet
operators do not regularly perform tire pressure maintenance to the
standards recommended by tire manufacturers. Improper inflation
increases total tire-related costs by an estimated \$600 to \$800
annually per tractor-trailer combination. [^2] At the time the study was
completed, diesel fuel cost approximately \$1.50 per gallon.

Many of the TPMS on the market today average between \$1,000 to \$1,500
per tractor-trailer. The conservative assumptions made in the 2003 study
estimated a payback period for many fleets is likely less than 2
years---and almost certainly less than 3 years for most fleets. Despite
this analysis, the market penetration rate of tire pressure maintenance
equipment has remained comparatively low in the intervening
period---fewer than 3 percent of for-hire fleets use tire pressure
monitoring technology in regular operations. While the negative
consequences of poor tire maintenance appear to be generally understood,
there has been a lack of objective, accurate, independently conducted
real-world test data concerning the effectiveness of current and
emerging technologies focused on improving and simplifying tire pressure
maintenance.

## Current State of Tire Pressure Technology Development

Over the past decade, there has been significant investment by equipment
suppliers serving the commercial vehicle market in tire pressure
monitoring and inflation systems. New products have been introduced,
other products have been refined, and (according to informal interviews
with fleets) the development efforts of these companies have
intensified. This section explores the current state of tire pressure
monitoring and maintenance technology development.

### Dual Tire Pressure Equalizers

Tire pressure equalizers are designed to balance the pressure between
the two tires of a dual assembly. Equalizing the tire pressure reduces
irregular tire wear and heat build up and decreases rolling resistance,
which improves fuel economy. By reducing the number of tire airing
points, they also reduce the time needed to check and maintain tire
pressure. Most systems also include a visual indicator to provide a
means for pressure monitoring.

Tire pressure equalizer systems balance pressure in dual tire
configurations by allowing air to transfer between tires. Two hoses are
plumbed to a check valve at one end and to the valve stems of each tire
at the other. The check valve is mechanically bolted to the hub of the
outer wheel. The valve opens to allow airflow between the tires, but
closes and shuts the air off if there is an instantaneous air loss in
either tire, which prevents both tires from going flat. In a slow leak
situation, the valve isolates (i.e., closes) both tires after a pressure
drop of approximately 10 psi. Exhibit 1.1 displays a simplified drawing
of a dual tire equalizer with the equalizing valve in the open position
and in the closed or isolating position. A spring and diaphragm assembly
provides the equalizer's functionality. The pressure level that causes
the valve to close to isolate the tires is set by the pressure required
to push the diaphragm off the valve seat of one of the tire lines. In
the example in Exhibit 1.1, the equalization pressure is 90 psi or
greater.

[]{#__RefHeading___Toc149980535 .anchor}Exhibit 1.1 -- Dual Tire
Equalizer Diagram

[![Exhibit 1.1 displays a simplified drawing of a dual tire equalizer
with the equalizing valve in the open position and in the closed or
isolating position.](media/image2.wmf){width="3.5519685039370077in"
height="1.5834645669291338in"}![Exhibit 1.1 displays a simplified
drawing of a dual tire equalizer with the equalizing valve in the open
position and in the closed or isolating
position.](media/image3.wmf){width="3.5625984251968505in"
height="1.75in"}](http://www.fmcsa.dot.gov/)

Because these devices have a central valve to serve both tires in the
dual assembly, they eliminate the need to check and add air to each tire
separately. These systems also provide a visual pressure indicator that
is visible to a driver during a pre-trip inspection. They generally do
not provide numerical inflation pressures, rather they provide different
types of go/no-go gauges that can indicate whether the tires are
under-inflated, over-inflated, or at the correct pressure. This display
feature is the primary difference between these systems and tire
pressure monitoring systems.

A problem with tire pressure equalizers, as reported by the informal
interviews conducted with fleets as part of the 2003 study, is that the
accuracy of the valves deteriorate as the internal diaphragms wear after
a year or two. Hose breakage is also a relatively high maintenance item.

### Tire Pressure Monitoring Systems

There are several types of tire pressure monitors. These systems can be
categorized into the following types:

-   Valve-stem-mounted tire pressure monitors

-   Wheel-mounted tire pressure monitors

-   Tire-mounted tire pressure monitors

These systems monitor tire pressure through a device that senses the
pressure and forwards an RF signal to a display unit. Displays may be
mounted inside the tractor cab, attached externally on the tractor or a
handheld off-board reader can be used. Some of these systems also
monitor temperature and convert the actual hot tire pressure to cold
pressure so that meaningful data is related to the user (i.e.,
temperature compensation is included). Exhibit 1.2 shows a typical
tractor trailer installation of a wheel-mounted tire pressure monitoring
system.

[]{#__RefHeading___Toc149980536 .anchor}Exhibit 1.2 -- Example
Wheel-Mounted Tire Pressure Monitoring System

![](media/image4.jpeg){width="4.08125in" height="3.173611111111111in"}

###  Tire Pressure Maintenance Systems

There are basically two types of tire inflation systems. The first type
uses air from the vehicle's air system to inflate the tires. These
systems are generally referred to as central tire inflation systems. The
second type uses a pump that is separate from the vehicle's air system
to generate air. These systems are referred to as continuous tire
pressure pumps.

Central tire inflation systems use the air stored in the vehicle's air
brake wet tanks to supply air to the tires. Manufacturers of such
systems use one of two general approaches for filling the tires with air
during dynamic conditions (while the tires are rotating). Both
approaches rely on the use of a rotating slip ring/seal arrangement. The
Gio-Set Vigia, shown in Exhibit 1.3, uses an air-filled rotary union
mounted externally on the center of the wheel hub.

[]{#__RefHeading___Toc149980537
.anchor}![](media/image5.jpeg){width="5.002777777777778in"
height="2.9430555555555555in"}Exhibit 1.3 -- Rotary Union Style CIS

An alternative approach, used by Arvin Meritor, uses the axle to deliver
air to the wheel with the rotary union located in the hubcap at each
wheel end, as shown in Exhibit 1.4.

[]{#__RefHeading___Toc149980538 .anchor}Exhibit 1.4 -- Hollow Axle Style
CIS

![](media/image6.png){width="3.953472222222222in"
height="2.5229166666666667in"}

Central tire inflations systems can supply air to the tires either on
demand via a manual request by the driver, or automatically triggered
through sensors that monitor tire pressure. Central tire inflation
systems can be broken down into two types---constant and variable.

***Constant central tire inflation systems*** maintain tire pressure at
a single preset level. They eliminate the need to check tire pressure
manually and allow a vehicle to remain in service despite small air
leaks in one or more of its tires. Constant tire inflation systems
require no involvement from the driver. They automatically sense the
pressure in the tires and inflate as necessary when the tires lose air.
A drawback to these systems is that the external hoses or air supply
tubes can get damaged and render the systems ineffective, and may even
allow tires to deflate suddenly. Also, the slip ring seal that allows
air to enter the rotating hub through the axle can become worn over
time. An additional drawback is that a slow leak, such as from a nail
hole through the tread, could go undetected because the inflation system
effectively "masks" the problem. Over time, the presence of the foreign
object could lead to tread separation.

***Variable central tire inflation systems*** are designed to raise or
lower tire pressures during vehicle operation to compensate for varying
load and road conditions, in addition to maintaining tire pressure.
These systems allow interaction from the driver such as changing the
tire pressure on demand. They are usually used for on-off road
operations such as logging, construction, mining, gravel hauling,
concrete, exploration, and military. The costs of these systems tend to
be higher than for tire pressure maintenance systems.

### Other Systems and Technologies

In response to the Firestone tire recall of 2000, new and innovative
systems and technologies are being explored to address the problem of
tire failures. Some of these technologies do not fit the general
category of tire pressure monitors, but do address detection of tire
failures. Appendix A provides a listing of several new TPMS and tire
failure monitoring technologies.

## Research Objectives

The primary objective of this research study was to document the
performance and operational characteristics of leading-edge commercial
vehicle TPMS.

This study focused on examining the ability of various TPMS to detect
tire pressure, temperature (for the purpose of converting to cold
pressure readings), and air leakage rates under a variety of test
conditions and in a controlled test track environment. The study team
examined inflation systems under dynamic conditions for their ability to
maintain tire pressure under various simulated leak conditions, as well
as performing selected failure mode tests of the systems. The study also
included a limited review of driver acceptance issues associated with
the various systems, and of reliability and maintenance issues. The
purpose of the test was to assess the relative performance of different
types of tire pressure monitoring and maintenance technologies, rather
than to compare various manufacturers' products.

This study should prove useful to fleet operators in evaluating the
capabilities and limitations of alternative TPMS approaches, and in
determining specifications for future truck purchases. The information
should also be useful to TPMS suppliers and commercial vehicle
manufacturers that are developing new tire monitoring and inflation
systems.

The following sections describe the specific objectives and questions
addressed by the study.

### Dual Tire Pressure Equalizers

The dual tire pressure equalizer research objectives for the program
were to:

-   Validate that pressure is equalized between the two tires if
    pressure drops in one tire.

-   Determine the time to equalize pressure under various test
    conditions.

-   Validate that the "isolating" valve will engage to protect the other
    (non-leaking) tire if one tire experiences significant pressure
    loss. Also, measure the pressure threshold that the isolation valve
    engages.

-   Determine what happens when one hose is not attached to a valve stem
    (simulating a cut hose).

-   Determine whether both tires can be inflated through the central
    valve stem.

-   Determine whether the indicator shows changes due to pressure loss
    (i.e., was there a visual indication?).

-   Observe the effects of weather (ambient temperature) on performance.

-   Determine whether the system works when the vehicle is parked as
    well as when it is in motion.

### Tire Pressure Monitoring Systems

The tire pressure monitoring system research objectives for the program
were to:

-   Determine at what pressure change an alert is sent to the in-cab
    monitor.

-   Determine the accuracy of the pressure monitor display (display
    readings versus actual readings), and the ability to display the
    correct wheel position and pressure on demand.

-   Determine whether the signal from the trailer can consistently reach
    the tractor's display.

-   Test the handheld reader for its accuracy and ability to read
    pressures. Determine the maximum distance between the handheld
    reader and the tire transmitter that allows data to be read.

-   Determine what happens when the valve stem is bent or the sensor is
    otherwise damaged.

-   Determine what happens if the sensor is removed or falls off the
    valve stem.

-   Observe the effects of the environment, such as temperature and
    rain, on performance.

-   Determine whether audio and visual display alerts are sufficient to
    notify drivers (e.g., loud enough, bright enough).

-   Determine whether the system advises the driver of failed sensors,
    missing sensors, or sensors that are operating with depleted
    batteries.

-   Determine whether the systems work when the vehicle is parked as
    well as when it is in motion.

-   For systems using gate readers, test to determine the maximum speed
    the signals from all wheel positions can be accurately sensed by the
    gate reader. Test the percentage and consistency of the reads.

-   Determine the system's response to the sensors separating from the
    valve, wheel, or tire.

### Tire Pressure Maintenance Systems

The tire pressure maintenance system research objectives for the program
were to:

-   Determine at what pressure the indicator light on the trailer is
    illuminated to signal air delivery to trailer tires, and at what
    pressure the driver is alerted (via the in-cab display) if tractor
    tires are being filled.

-   Determine the system's ability to correct low inflation conditions.

-   Determine what happens when an air line is not connected to the
    valve stem (simulate cut hose).

-   Determine whether pressure is equalized between both tires if
    pressure drops in one tire.

-   Determine at what pressure the bypass valve closes to protect an
    intact tire if another tire suffers a rapid air loss.

-   Determine whether the pressure in the brake system is maintained
    during a "catastrophic" air loss situation in a tire.

-   Observe the effects of ambient air temperature on performance.

-   Determine whether the system works when parked as well as when in
    motion.

## Overview of Experimental Approach

The team installed the various tire pressure monitoring and inflation
systems in a planned sequence on two types of commercial motor
vehicles---first, on a conventional tractor-trailer, and then on a
motorcoach---and tested them under controlled operating conditions on a
test track. All work was conducted at the TRC in Columbus, OH. The study
team considered installing all of the sensor systems on the vehicle at
the same time, and then conducting each test (simulated leaks, failure
modes, etc.) in sequence. Such an arrangement would have ensured that
all of the TPMS were examined under identical conditions. However, such
an arrangement was not feasible. For example, two RF systems cannot be
operated side by side at the same time because of the possibility of
interference between the two systems. Similarly, it is not possible to
connect and test two equalizing systems on the same wheel end at the
same time due to lack of space and the inability to determine which
system was influencing the pressure in the tires. Fortunately,
technicians and engineers at TRC have considerable experience with
conducting tests under consistent and repeatable conditions and the test
conditions for all "runs" in the test matrix were tightly controlled.

The team recorded data from the TPMS using an on-board, PC-based
data-logging system capable of recording digital, analog, and discrete
sensor outputs. (This system is described in more detail in Chapter 3.)
The team then processed the data off-board using conventional database
and engineering analysis software.

# DESCRIPTION OF Tested Systems

The study team selected representative products from within the three
categories of TPMS (tire equalization, tire pressure monitoring, and
automatic inflation) for testing, as shown in Exhibit 2.1. Tested
products included two dual tire equalizers, four tire pressure
monitoring systems, and two tire pressure maintenance systems (central
inflation systems only since hub-mounted tire pressure pumps are
currently unavailable). The selected systems represented a reasonable
cross-section of technological approaches to tire pressure monitoring
and inflation. All systems tested are commercially available, and none
were prototypes.

[]{#__RefHeading___Toc149980539 .anchor}Exhibit 2.1 -- Selected Systems
for Testing

+---------------------+-----+------+------+-------------------------+
| **Technology**      | **  | **T  | **M  | **Recommended System    |
|                     | Tra | rail | otor | for Testing**           |
|                     | cto | er** | -Coa |                         |
|                     | r** |      | ch** |                         |
+---------------------+-----+------+------+-------------------------+
| Dual Tire           |     |      |      |                         |
| Equalizers          |     |      |      |                         |
+---------------------+-----+------+------+-------------------------+
| Equalizing Systems  | X   | X    |      | Cat's Eye               |
| #1                  |     |      |      |                         |
|                     |     |      |      | (Link Manufacturing,    |
|                     |     |      |      | Ltd.)                   |
+---------------------+-----+------+------+-------------------------+
| Equalizing Systems  | X   | X    |      | Tire-Knight-S           |
| #2                  |     |      |      |                         |
|                     |     |      |      | (V-Tech International,  |
|                     |     |      |      | Inc.)                   |
+---------------------+-----+------+------+-------------------------+
| Tire Pressure       |     |      |      |                         |
| Monitoring Systems  |     |      |      |                         |
+---------------------+-----+------+------+-------------------------+
| Direct Monitoring   | X   | X    |      | PressurePro             |
| System #1           |     |      |      |                         |
|                     |     |      |      | (Advantage PressurePro, |
| (valve stem         |     |      |      | LLC)                    |
| mounted)            |     |      |      |                         |
+---------------------+-----+------+------+-------------------------+
| Direct Monitoring   |     |      | X    | Integrated Vehicle Tire |
| System #2           |     |      |      | Pressure Monitoring     |
|                     |     |      |      | (Meritor WABCO)         |
| (valve stem         |     |      |      |                         |
| mounted)            |     |      |      |                         |
+---------------------+-----+------+------+-------------------------+
| Direct Monitoring   | X   | X    |      | Tire-SafeGuard          |
| System #3           |     |      |      |                         |
|                     |     |      |      | (HCI Corporation)       |
| (wheel mounted)     |     |      |      |                         |
+---------------------+-----+------+------+-------------------------+
| Direct Monitoring   |     |      | X    | SmarTire                |
| System #4           |     |      |      |                         |
|                     |     |      |      | (SmarTire Systems,      |
| (wheel mounted)     |     |      |      | Inc.)                   |
+---------------------+-----+------+------+-------------------------+
| Direct Monitoring   | X   | X    |      | eTire                   |
| System #5           |     |      |      |                         |
|                     |     |      |      | (Michelin North         |
| (tire mounted)      |     |      |      | America)                |
+---------------------+-----+------+------+-------------------------+
| Tire Pressure       |     |      |      |                         |
| Maintenance Systems |     |      |      |                         |
+---------------------+-----+------+------+-------------------------+
| Central Inflation   |     | X    |      | PSI Tire Inflation      |
| System #1           |     |      |      | System                  |
|                     |     |      |      |                         |
|                     |     |      |      | (Arvin Meritor)         |
+---------------------+-----+------+------+-------------------------+
| Central Inflation   |     |      | X    | Vigia                   |
| System #2           |     |      |      |                         |
|                     |     |      |      | (Gio-Set Corporation)   |
+---------------------+-----+------+------+-------------------------+

The following is a brief explanation for including each of these systems
in the test plan:

-   Cat's Eye (Link Manufacturing, Ltd.) is a dual-tire equalizer with a
    visual inflation condition reading at the wheel end.

-   Tire-Knight-S (V-Tech International, Inc.) is a uniquely designed
    dual-tire equalizer system. The Tire-Knight-S has separate valves
    and chambers for inflating and checking each tire separately.

-   PressurePro (Advantage PressurePro) is a representative
    valve-stem-mounted tire pressure monitor using an in-cab display.

-   Integrated Vehicle Tire Pressure Monitoring, or IVTM, system
    (Meritor WABCO) is a valve-stem-mounted tire pressure monitor
    developed cooperatively between Michelin and Meritor WABCO for
    commercial vehicles.

-   Tire-SafeGuard (HCI Corporation) is a representative wheel-mounted
    tire pressure monitor with in-cab display.

-   SmarTire (SmarTire Systems, Inc.) produces a wheel-mounted tire
    pressure monitoring systems for light-duty vehicles. They have
    recently launched a similar system for commercial vehicles and are
    marketing it through original equipment manufacturers (OEMs).

-   eTire (Michelin North America) is a passive tag, tire-mounted
    pressure monitoring system. Unlike the other monitoring systems, it
    does not have an in-cab display but uses a gate reader and/or
    handheld reader to read the tire pressures.

-   PSI Tire Inflation System (Arvin Meritor) is a representative
    central tire inflation system for trailers.

-   Vigia (Geo-Set Corporation) is new to the North American market but
    has been used for many years in Central and South America. The
    system is unique in that it can be installed on both non-drive and
    drive axles.

The project team recommended testing each of these systems on the
proposed platforms in Exhibit 2.1, as they presented a good combination
of representative systems and emerging technologies for the commercial
vehicle industry. The following sections briefly describe each of the
selected systems.

## Dual Tire Equalizers

**Link Manufacturing, Ltd.** produces the ***Cat's Eye Tire Pressure
Maintenance System***[^3] shown in Exhibit 2.2. A solid yellow
indication on the air valve indicates that the tire pressure is +/- 2
percent of the recommended inflation level. As the pressure drops, a
vertical black line, the "Cat's Eye," appears in the center of the
display. As pressure drops further, the line widens until an all-black
display indicates that tire pressure is approximately 10 psi below the
specified level. The display is factory set for a specific pressure and
is non-adjustable. This system currently costs about \$50 an axle end to
the end-user with rubber hoses, and \$60 an axle end with stainless
steel hoses. The company has been marketing the Cat's Eye Tire Pressure
Maintenance System since 1990, and estimates that it has sold 125,000
units to date. It now sells approximately 30,000 annually.

[]{#__RefHeading___Toc149980540 .anchor}![Exhibit 2.2 shows the Link
Manufacturing, Ltd. produces the Cat's Eye Tire Pressure Maintenance
System. Two hoses are connected to the indicator body. A detail of the
indicator shows A solid yellow indication on the air valve indicates
that the tire pressure is +/- 2 percent of the recommended inflation
level. A vertical black line, the "Cat's Eye," appears in the center of
the display and widens as the pressure drops
.](media/image7.png){width="3.144488188976378in"
height="2.3653543307086613in"}![Exhibit 2.2 shows the Link
Manufacturing, Ltd. produces the Cat's Eye Tire Pressure Maintenance
System. Two hoses are connected to the indicator body. A detail of the
indicator shows A solid yellow indication on the air valve indicates
that the tire pressure is +/- 2 percent of the recommended inflation
level. A vertical black line, the "Cat's Eye," appears in the center of
the display and widens as the pressure drops
.](media/image8.png){width="2.983464566929134in"
height="2.283464566929134in"}Exhibit 2.2 -- Link Cat's Eye TPMS
Dual-Tire Equalizer

**V-Tech International, Inc.** produces the ***Tire-Knight-S*** for
dual-truck tires.[^4] It is similar to the Link system described above
and to other equalizer systems, using a check valve assembly mounted on
the wheel with hoses attached to the valve stems of both dual tires.
Exhibit 2.3 displays the V-Tech Tire-Knight-S Equalizer system. However,
in the Tire-Knight-S system, each tire is connected to its own chamber
and has its own valve for individual inflating and pressure checking in
the unit. A bypass connects and equalizes the pressure in both tires
when a piston opens or closes the bypass. (The piston is the only moving
part in the unit.) The piston opens the bypass if both tires have a
pressure greater than 85 to 90 psi. The piston closes the bypass if one
tire experiences a sudden and catastrophic air loss, if one hose is
unhooked or cut, or if both tires have a pressure of less than 80 to 85
psi. The position of the piston can be checked at a glance. In the event
of an air loss in one tire of a pair of duals, the system configured as
tested would not indicate which is leaking. V-Tech stated it has sold
about 100 to 200 units in the Wisconsin area, including some to a major
truckload motor carrier headquartered in that state. The retail price
per unit is \$80, or \$640 for 16 positions.

[]{#__RefHeading___Toc149980541 .anchor}![Exhibit 2.3 displays the
V-Tech Tire-Knight-S Equalizer system which uses a check valve assembly
mounted on the wheel with hoses attached to the valve stems of both dual
tires. A close up view shows that each tire has its own valve for
individual inflating and pressure checking in the unit.
](media/image9.png){width="4.177952755905512in"
height="2.2456692913385825in"}![Exhibit 2.3 displays the V-Tech
Tire-Knight-S Equalizer system which uses a check valve assembly mounted
on the wheel with hoses attached to the valve stems of both dual tires.
A close up view shows that each tire has its own valve for individual
inflating and pressure checking in the unit.
](media/image10.png){width="2.608267716535433in"
height="1.6125984251968504in"}Exhibit 2.3 -- V-Tech Tire-Knight-S
Dual-Tire Equalizer

## Tire Pressure Monitors

**Advantage PressurePro LLC** markets ***PressurePro*** (formerly known
as Tire Mate).[^5] The company began its entry into the tire pressure
monitor market in 1992 with a device called Tire Mate, which fits over
the valve stem like a valve cap and transmits an RF signal indicating
the tire pressure.

The company's current product is called PressurePro*.* It is
approximately 1 inch in diameter and ¾ inch in length, weighs 0.25
ounce, is completely sealed, and fits over the valve stem. Exhibit 2.4
displays the Advantage PressurePro TPMS valve-stem-mounted unit and
display console. There is no RF "cross-talk" between systems on adjacent
wheels as each sensor signal is uniquely identified by its own serial
code. The sensors check tire pressure every 15 seconds. The PressurePro
system can monitor 1 to 34 tires with pressure from 10 to 150 psi. The
target pressure is set at the current tire pressure at the time of
installation of the sensor on the valve stem.

The receiver/monitor is battery operated. The monitor is 6 inches wide x
3 inches tall and

0.5 inch thick, and weighs just under 8 ounces. When tire pressure drops
below the low trigger pressure set by the user, the monitor triggers an
alert that displays tire location, low pressure reading, and battery
power in the sensor. An audio and visual alert comes on when a tire is
10 percent below target pressure, and a more aggressive alert identifies
a tire that is 20 percent below. The driver can scroll through the
display to check all tires on demand as well. The battery life in the
valve-stem sensors is expected to be 5 years in automobiles, 3 to 3.5
years in RV applications, and 2 years on commercial trucks. The life of
the battery is dependent upon mileage since the sensor is activated by
tire rotation. The RF signals from the trailer tires are linked to the
tractor receiver with a relay box that fits on the front of the trailer
and sends an RF signal to the cab.

Alternatively, a handheld receiver called the PressurePro Wand can read
sensors within one foot of the tire. A gate reader will be added to the
product line as well. PressurePro is currently being field tested. The
company has 600 units installed on a variety of commercial vehicles. The
cost for an 18-wheel, tractor-trailer combination will be around \$1,075
for the sensors and on-board receiver. Between 35,000 and 40,000 Tire
Mate units have been sold, primarily to the RV industry and
owner-operators. Advantage estimates that about 600 to 800 of the new
PressurePro systems are operating on commercial vehicles at this time.

[]{#__RefHeading___Toc149980542 .anchor}![Exhibit 2.4 displays two of
the wheel-mounted module that screw onto the valve stems and the
dashboard display with antenna attached of the Advantage PressurePro
TPMS system. The display has a representation of the truck to indicate
wheel positions and pressures with LEDs as well as several membrane type
buttons to interface with the
system.](media/image11.png){width="4.211811023622047in"
height="2.1818897637795276in"}![Exhibit 2.4 displays two of the
wheel-mounted module that screw onto the valve stems and the dashboard
display with antenna attached of the Advantage PressurePro TPMS system.
The display has a representation of the truck to indicate wheel
positions and pressures with LEDs as well as several membrane type
buttons to interface with the
system.](media/image12.png){width="0.9874015748031496in"
height="0.989763779527559in"}![Exhibit 2.4 displays two of the
wheel-mounted module that screw onto the valve stems and the dashboard
display with antenna attached of the Advantage PressurePro TPMS system.
The display has a representation of the truck to indicate wheel
positions and pressures with LEDs as well as several membrane type
buttons to interface with the
system.](media/image13.png){width="0.9007874015748032in"
height="1.0062992125984251in"}Exhibit 2.4 -- Advantage PressurePro TPMS

**Meritor WABCO** and **Michelin** developed the ***WABCO Integrated
Vehicle Tire Pressure Monitoring (IVTM) System*** for commercial
vehicles.[^6] The IVTM system was launched in 2003; no unit sales
numbers are available at this time. Each tire and wheel assembly is
equipped with a wheel module that is attached to the outside of the
wheel rim using two wheel bolts and nuts. It is connected to the tire
valves using pneumatic hoses. Exhibit 2.5 displays the wheel-mounted
module and dashboard display of the WABCO IVTM system. The system checks
pressure constantly and transmits tire pressure via an RF signal every
15 minutes to the electronic control unit (ECU) if tire pressure remains
in the target range, or every 30 seconds if a tire exhibits a loss of
pressure variation. RF operating frequency is 433 MHz. Power is supplied
from a built-in lithium battery with a 5-year service life.

The IVTM ECU is mounted on the vehicle chassis attached equidistant
between the front/rear axles and contains a built-in antenna to receive
the pressure data from all tires. According to the manufacturer, this
location eliminates the need for additional antennas in the wheel
modules themselves. Trailers are equipped with their own
ECU/transmitter, which sends the tire inflation pressure RF signals to
the ECU on the tractor.

The dashboard-mounted display warns the driver optically and
acoustically when the inflation pressure of a tire on the tractor or
trailer has decreased to a critical value. A yellow lamp indicates a
slow rate of pressure loss or slight decrease in pressure; a red lamp
indicates extremely low pressure. The position of any instrumented tire
can be selected and its inflation pressure can be queried at the push of
a button. If all tires are within an appropriate inflation pressure
range, the display is blank.

[]{#__RefHeading___Toc149980543 .anchor}![Exhibit 2.5 displays the
wheel-mounted module attached to a wheel via the lug bolts and the
dashboard display of the WABCO IVTM system. The display has a
representation of the truck to indicate wheel positions and pressures
with LEDs as well as several membrane type buttons to interface with the
system.](media/image14.jpeg){width="3.5228346456692914in"
height="2.5346456692913386in"}![Exhibit 2.5 displays the wheel-mounted
module attached to a wheel via the lug bolts and the dashboard display
of the WABCO IVTM system. The display has a representation of the truck
to indicate wheel positions and pressures with LEDs as well as several
membrane type buttons to interface with the
system.](media/image15.jpeg){width="3.052755905511811in"
height="2.5346456692913386in"}Exhibit 2.5 -- WABCO Integrated Vehicle
Tire Pressure Monitoring TPMS

**HCI Corporation** manufactures the ***Tire-SafeGuard*** tire pressure
monitoring system.[^7] This system alerts drivers of low-pressure
situations by providing the location, temperature, and pressure readings
via a display unit and an audible signal. The system has been on the
market since 1991, and there are approximately 20,000 units in
operation. Exhibit 2.6 displays the wheel-mounted sensor and driver's
display of the Tire-SafeGuard TPMS. It monitors tire pressure
continuously with detection of abnormal tire pressure even while the
vehicle is parked. The Tire-SafeGuard product for commercial vehicles
(TPM-S206) uses a sensor mounted on the wheel rim inside the tire. The
low-pressure and temperature warning is user adjustable and has a range
of 18 to 130 psi. The sensor transmitter automatically switches on when
the vehicle is moving faster than 15 mph and reports pressure readings
to the receiver using an RF signal. Pressure measurement accuracy is
said to be +/- 1 psi. The sensor module has an operating temperature
range of -40 to 250 degrees and a battery life of over 5 years. The
receiver for the display can be plugged into a 12 VDC auxiliary power
outlet or can be directly hardwired to the main power source. It is 3 ½
x 1 ^1^/~8~ x ^5^/~8~ inches in size and weighs 1.5 ounces. The cost to
equip a tractor

(10 positions) is \$650 or \$1,245 for a tractor-trailer (18 positions).

[]{#__RefHeading___Toc149980544 .anchor}![Exhibit 2.6 displays the
wheel-mounted sensor and driver's display of the Tire-SafeGuard TPMS.
The wheel-mounted sensor attaches to the interior of the wheel rim with
a large hose clamp around the rim. The display has a representation of a
truck to indicate wheel positions and pressures with LCDs as well as a
button to interface with the
system.](media/image16.jpeg){width="3.3763779527559055in"
height="1.5846456692913387in"}![Exhibit 2.6 displays the wheel-mounted
sensor and driver's display of the Tire-SafeGuard TPMS. The
wheel-mounted sensor attaches to the interior of the wheel rim with a
large hose clamp around the rim. The display has a representation of a
truck to indicate wheel positions and pressures with LCDs as well as a
button to interface with the
system.](media/image17.jpeg){width="3.0255905511811023in"
height="1.5744094488188976in"}Exhibit 2.6 -- HCI Tire-SafeGuard TPMS

**SmarTire Systems, Inc**. [^8] SmarTire's system in the marketplace at
the time of this study uses RF transmission of data to monitor the air
pressure and temperature in tires. A small sensor is strapped on each
wheel and collects temperature and pressure data every 7 seconds. This
data is transmitted via radio frequency to a receiver display located
inside the vehicle that indicates individual tire pressure and
temperature. Exhibit 2.7 displays the display and wheel-mounted sensor
of the SmarTire system. The transmitted tire data is captured by the
receiver mounted in the cab, which in turn sends the information to the
display unit. The display unit allows the driver to toggle through each
wheel position and to select the type of information being
displayed---tire pressure, temperature, or pressure deviation. The
display incorporates a bright red LED light, which is activated whenever
a tire pressure irregularity is detected or when the temperature of a
tire goes above a preset level. SmarTire currently sells tire-monitoring
products for the RV vehicle market and for the CMV market and has had
systems available on the market since 1985 (no unit sales numbers are
available). These products monitor pressures up to 188 psi and
accommodate up to 20 wheel positions. The cost for a motorcoach
installation is \$1,074

(8 positions).

[]{#__RefHeading___Toc149980545 .anchor}![Exhibit 2.7 displays the
display and wheel-mounted sensor of the SmarTire system. The
wheel-mounted sensor attaches to the interior of the wheel rim with a
large hose clamp around the rim. The display has a representation of a
truck to indicate wheel positions and pressures with LCDs as well as a
buttons and a warning light to interface with the
system.](media/image18.png){width="2.9708661417322832in"
height="1.7929133858267716in"}![Exhibit 2.7 displays the display and
wheel-mounted sensor of the SmarTire system. The wheel-mounted sensor
attaches to the interior of the wheel rim with a large hose clamp around
the rim. The display has a representation of a truck to indicate wheel
positions and pressures with LCDs as well as a buttons and a warning
light to interface with the
system.](media/image19.jpeg){width="1.941732283464567in"
height="1.6700787401574804in"}Exhibit 2.7 -- SmarTire TPMS

**Michelin North America** introduced its **eTire** system for
medium-duty trucks in October 2002. [^9] The eTire system uses
Michelin's battery-less InTire Sensors that the manufacturer states can
be applied to any commercial truck tire using sidewall-mounted
"SensorDocks," which are molded rubber pieces that chemically cure to
the inside of the sidewalls, similar to tire sidewall repair units. The
sensor unit slips over a knob on the rubber dock and locks into place.
Once installed, the sensors are designed to last throughout the entire
life of the tire carcass, including retread processes. The sensor is
also designed to be removable and reused on a different truck tire
equipped with a new SensorDock. The sensors measure temperature and
pressure on demand and communicate this information along with wheel
position, and a programmable identification number for its respective
tire, to drive-by and handheld readers that power the sensors. Other
sensors located on the tractor and trailer provide vehicle
identification information at the same time. The sensors include an RF
transmitter, pressure and temperature sensors, and an antenna, which are
encased in impact- and heat-resistant plastic. The unit measures 4 x 1.5
inches and weighs less than an ounce. Exhibit 2.8 displays the Michelin
eTire TPMS system components including the sensor, handheld reader, and
gate reader installation.

Unlike the other systems, e-Tire does not use an in-cab display.
Instead, readings are taken when the vehicle passes a gate reader or by
using a handheld reader. The vehicle must travel about 5 mph or less for
the gate reader to receive the information from all the tire sensors.
The sensors include a temperature compensation function. The information
gathered for each fleet is reported via the Internet to a Michelin file
server. The fleet accesses Michelin's BIBTRACK web site that tracks
tires and provides recommended actions to be taken on tires identified
that require pressure adjustment. Fleets can get up-to-date information
on their tires, track tire costs, and monitor inventories around the
clock by going on-line. No data is stored on the sensors themselves. The
InTire Sensors do not have 360-degree read capability so the handheld
reader must be positioned over the sensor to read it. Michelin places an
eTire label on the outside of the tire that visually locates the sensor.
Each sensor unit costs about \$30, but actual fleet cost will vary based
on fleet size. Handheld readers are approximately \$6,000, and gate
readers are approximately \$10,000 to \$12,000. No unit sales numbers
are available.

[]{#__RefHeading___Toc149980546 .anchor}![Exhibit 2.8 displays the
Michelin eTire TPMS system components including the sensor, handheld
reader and gate reader installation. The tire sensor is shown mounted to
the interior sidewall of the tire and the test truck is show driving
between the gate
sensors.](media/image20.jpeg){width="2.766535433070866in"
height="1.95in"}![Exhibit 2.8 displays the Michelin eTire TPMS system
components including the sensor, handheld reader and gate reader
installation. The tire sensor is shown mounted to the interior sidewall
of the tire and the test truck is show driving between the gate
sensors.](media/image21.jpeg){width="1.4374015748031497in"
height="3.1291338582677164in"}![Exhibit 2.8 displays the Michelin eTire
TPMS system components including the sensor, handheld reader and gate
reader installation. The tire sensor is shown mounted to the interior
sidewall of the tire and the test truck is show driving between the gate
sensors.](media/image22.png){width="3.101574803149606in"
height="1.1661417322834646in"}![Exhibit 2.8 displays the Michelin eTire
TPMS system components including the sensor, handheld reader and gate
reader installation. The tire sensor is shown mounted to the interior
sidewall of the tire and the test truck is show driving between the gate
sensors.](media/image23.jpeg){width="2.7681102362204726in"
height="1.8362204724409448in"}Exhibit 2.8 -- Michelin eTire TPMS

## Automatic Inflation Systems

**Arvin Meritor** distributes **Pressure System International's (PSI's)
*Tire Inflation System***.[^10] This system currently addresses only
trailer tires but the company stated that it was working on developing a
system for tractors during the time the tests were conducted. Since
1994, 500,000 units have been sold, with the manufacturer reporting an
average of 30,000 to 40,000 in annual sales. The Tire Inflation System
uses compressed air from the trailer to inflate any tire that falls
below pre-defined specifications. Air from the existing trailer supply
tank for the air brakes is routed to a control box and then into each
axle (see Exhibit 2.9). The hollow trailer axles carry the air through a
rotary union assembly at the spindle end, which then distributes the air
to each tire as needed. Tire pressure is constantly monitored. When a
tire experiences a leak, an indicator light mounted on the trailer in a
position visible by the driver's mirror comes on to signal air delivery
and that tires are being inflated. A one-way check valve located in the
hose connected to the valve stem protects each tire against air pressure
loss. If a tire is punctured during operation and loses air pressure,
the check valve prevents loss of pressure in the other tires. A pressure
protection valve located between the shut-off valve and the reservoir
allows air to flow to the tire inflation system only when the brakes
have sufficient pressure to operate correctly. The estimated cost for
this system is approximately \$350 to \$400.

[]{#__RefHeading___Toc149980547 .anchor}Exhibit 2.9 -- Arvin Meritor PSI
Tire Inflation System

![](media/image6.png){width="4.405555555555556in"
height="2.790277777777778in"}

**Gio-Set Corporation** produces the ***Vigia Automatic Tire Pressure
System*** for tractor-trailer combinations and RVs.[^11] This system
continuously reports and automatically regulates tire pressure. When the
pressure falls 2 to 3 psi in one or more tires, the Vigia system reports
the existence and location of the problem to the driver via an in-cab
display. At the same time, the inflation process starts to correct the
pressure loss. In case of a tire blowout, the equipment automatically
shuts down to protect the operation of the other air-powered components
on the vehicle such as the brakes, clutch, suspension, etc. Air pressure
is supplied from the secondary air reservoir. A dedicated air filter
absorbs the impurities in the air from the secondary reservoir. Once the
air is filtered, it reaches the control panel and from there is
redistributed to the tires (see Exhibit 2.10). A small control panel in
the truck cab controls all the functions in the system. The lights
indicate the normal function of the equipment, the loss of pressure in
tires, the air circuit where the loss is taking place, and the low air
pressure of the compressor. A separate control panel is placed on the
front corner of the trailer so that the driver can readily see it. This
system costs \$2,300 to \$3,200 depending on the axle setup for a
tractor and trailer combination. The Vigia system was first marketed in
1975 in South America, and 250,000 units have been sold in

15 countries.

[]{#__RefHeading___Toc149980548 .anchor}Exhibit 2.10 -- Gio-Set Vigia
Automatic Tire Pressure System

![Exhibit 2.10 shows the components of the Gio-Set Corporation Vigia
Automatic Tire Pressure System for tractor-trailer combinations and RVs.
Threre is a picture of the two rear axles of a bus with the hoses and
rotary unions on the hubs and a picture of the small control panel with
three gauges that indicate axle
pressures.](media/image24.jpeg){width="3.14251968503937in"
height="1.7692913385826772in"}![Exhibit 2.10 shows the components of the
Gio-Set Corporation Vigia Automatic Tire Pressure System for
tractor-trailer combinations and RVs. Threre is a picture of the two
rear axles of a bus with the hoses and rotary unions on the hubs and a
picture of the small control panel with three gauges that indicate axle
pressures.](media/image25.jpeg){width="3.37007874015748in"
height="2.558267716535433in"}

# TEST HARDWARE AND SETUP

All TPMS were installed on the test vehicles per manufacturers'
recommendations and instructions. The test vehicles were also equipped
with a data acquisition system and other instrumentation such as
fifth-wheel sensors, thermocouples, and pressure transducers. After
installation, all systems were calibrated according to the
manufacturers' instructions. This chapter provides specifics on the test
platform and instrumentation used to acquire, store, and analyze data
for the study. TRC completed all test activities related to vehicle
setup, instrumentation installation, and data acquisition setup and
programming.

## Test Platforms

The test vehicles were a 2001 Freightliner FLD tractor, shown in Exhibit
3.1, coupled to a 2001 Utility Trailer Manufacturing Co. 2000S tandem
axle flatbed semi-trailer and a 2003 MCI motorcoach, shown in Exhibit
3.3. The flatbed trailer design provided easy loading and unloading with
a forklift. Concrete blocks (4,300 pounds each) were chained to the deck
of the semi-trailer to achieve an 80,000-pound maximum gross combination
weight rating (GCWR). Exhibit 3.2 provides detailed specifications on
the tractor and trailer. Exhibit 3.4 provides detailed specifications on
the motorcoach.

[]{#__RefHeading___Toc149980549 .anchor}Exhibit 3.1 -- Tractor/Trailer
Test Platform

![](media/image26.png){width="6.5in" height="1.7652777777777777in"}

[]{#__RefHeading___Toc149980550 .anchor}Exhibit 3.2 -- Tractor/Trailer
Specification

  ---------------- -------------- ---------- ---------------- ------------- ----------- --------- ------------- -------------
  **TRACTOR**                                                 **TRAILER**                                       

  Tractor Make     Freightliner                               Trailer Make              Utility                 
                   FLD                                                                  2000S                   

  Model Year       2001                                       Model Year                2001                    

  Transmission     Meritor                                    Suspension                Spring                  
                   10-speed                                                                                     
                   Manual                                                                                       

  Front Suspension Spring                                     Length (feet)             48                      

  Rear Suspension  Spring                                     Wheelbase                 477                     
                                                              (inches)                                          

  GVWR (pounds)    80,000                                                                                       

  **TEST TIRES**                                                                                                

                   **Steer**                 **Intermediate                                       **Trailer**   
                                             /Rear Drive**                                                      

  Manufacturer     Bridgestone               Bridgestone                                          Bridgestone   

  Make/Type        R250                      M726                                                 R195          

  Size             295/75R22.5               295/75R22.5                                          295/75R22.5   

  Pressure (psi)   100                       100                                                  100           

  **WEIGHT                                                                                                      
  DISTRIBUTION**                                                                                                

                   **Steer Axle** **Drive                                   **Trailer                           **Total**
                                  Tandem**                                  Axles**                             

  GAWR/GCWR        12,500         38,000                                    40,000                              80,000

  Loaded w/Trailer 11,950         33,640                                    34,030                              79,620

  Empty w/Trailer  11,410         13,280                                    8,920                               33,610

  Bobtail          11,210         8,350                                     N/A                                 19,560
  ---------------- -------------- ---------- ---------------- ------------- ----------- --------- ------------- -------------

[]{#__RefHeading___Toc149980551 .anchor}Exhibit 3.3 -- Motorcoach Test
Platform

![](media/image27.jpeg){width="6.5in" height="1.511111111111111in"}

[]{#__RefHeading___Toc149980552 .anchor}Exhibit 3.4 -- Motorcoach
Specification

  ---------------- --------- ------------- ----------- ------------- ----------- ------------- -------------
  **MOTORCOACH**                                                                               

  Coach Make/Model           MCI/102EL3                                                        
                             E-Coach                                                           

  Model Year                 2001                                                              

  Transmission               Alison                                                            
                             5-speed                                                           
                             Automatic                                                         

  Front Suspension           Air                                                               

  Rear Suspension            Air                                                               

  GVWR (pounds)              50,000                                                            

  **TEST TIRES**                                                                               

  []{.mark}                  **Steer**                 **Drive**                 **Tag**       

  Manufacturer               Bridgestone               Bridgestone               Bridgestone   

  Make/Type                  R296                      R296                      R296          

  Size                       315/80R22.5               315/80R22.5               315/80R22.5   

  Pressure (psi)             110                       110                       105           

  **WEIGHT                                                                                     
  DISTRIBUTION**                                                                               

  []{.mark}        **Steer                 **Drive**                 **Tag                     **Total**
                   Axle**                                            Axles**                   

  GAWR/GVWR        15,900                  19,240                    14,520                    49,660
  ---------------- --------- ------------- ----------- ------------- ----------- ------------- -------------

## Test Instrumentation Installation

To acquire highly accurate pressure and temperature measurements (i.e.,
to establish "ground truth" against which readings from the various test
article could be compared), laboratory grade sensors were installed at
each test wheel position. This required removing the wheels, machining
replacement wheels for mounting thermocouples and pressure taps, and
routing wire bundles to the data acquisition system (DAS) mounted in the
cab of the truck and motorcoach. Exhibit 3.5 shows a diagram of a
tractor-trailer and motorcoach and illustrates the installation location
of each of the instrumentation packages.

[]{#__RefHeading___Toc149980553 .anchor}Exhibit 3.5 -- Instrumentation
Locations

  --------------- ---------------------- --------------- -----------------------
  **Reference**   **Location**           **Reference**   **Location**

  LFS             Left front steer       LFOT            Left front outer
                                                         trailer

  RFS             Right front steer      LFIT            Left front inner
                                                         trailer

  LFOD            Left front outer drive RFIT            Right front inner
                                                         trailer

  LFID            Left front inner drive RFOT            Right front outer
                                                         trailer

  RFID            Right front inner      LROT            Left rear outer trailer
                  drive                                  

  RFOD            Right front outer      LRIT            Left rear inner trailer
                  drive                                  

  LROD            Left rear outer drive  RRIT            Right rear inner
                                                         trailer

  LRID            Left rear inner drive  RROT            Right rear outer
                                                         trailer

  RRID            Right rear inner drive RTAG            Right tag axle

  RROD            Right rear outer drive LTAG            Left tag axle
  --------------- ---------------------- --------------- -----------------------

Test equipment consisted of:

-   Internal tire temperature thermocouples (9, analog)

-   Tire pressure transducers (2, analog)

-   Custom dual-flow combination rotary union and slip ring assemblies
    (5)

-   Custom pressure control manifold (1)

-   Primary and secondary brake reservoir and treadle valve pressure
    transducer (3, analog)

-   Digital marker switch (for indicating when a warning was observed)
    (1, analog)

-   Non-contact fifth wheel (1, digital)

-   DAS (1)

The following sections briefly describe this equipment.

### Thermocouples

Type J thermocouples, with a range of -200 to 320 degrees Fahrenheit,
were installed in each of the test wheels (9 wheels for the
tractor-trailer and 4 wheels for the motorcoach) as shown in Exhibit
3.6. The thermocouples were used to assist in evaluating the systems,
particularly understanding the effects of increased tire pressure as a
result of heating due to sustained high-speed driving. Additionally, the
thermocouples provided a temperature reference to evaluate the
performance of the systems under both normal and high-temperature
conditions and to provide insight to the conditions in the tires during
testing.

This approach involved attaching the slip ring/rotary union assembly to
the center of each instrumented wheel. A thermocouple was attached to
the slip ring and fed into the wheel using a threaded connection
separate from the normal valve stem. The voltage levels from the slip
rings were fed into the data acquisition system.

[]{#__RefHeading___Toc149980554 .anchor}Exhibit 3.6 -- Tire Temperature
Thermocouples and Pressure Lines

![](media/image28.jpeg){width="4.678472222222222in"
height="3.509027777777778in"}

### Tire Pressure Transducers

To perform the analysis, it was necessary to continuously monitor
internal tire pressure in tires under test using a reference transducer
at a data rate of 10 Hz. Pressure transducers, displayed in Exhibit 3.7,
were connected to a tee in the pressure line in the control manifold.
The pressure transducers were a 2-wire transmitter with a 0 to 200 psi
range and a 0.5-percent accuracy rating.

[]{#__RefHeading___Toc149980555 .anchor}Exhibit 3.7 -- Pressure
Transducer

![](media/image29.jpeg){width="2.696527777777778in"
height="1.7097222222222221in"}

### Custom Dual-Flow Rotary Union and Slip Ring Assemblies

During the development of the test matrix and test procedures, it became
apparent that an instrumentation package was needed to allow test
engineers to monitor and adjust tire pressure within the tire and wheel
assemblies while the vehicle was in motion (i.e., to simulate a
puncture). The team considered using wireless RF-type pressure
monitoring systems, but did not due to concerns of possible interference
with the RF-based TPMS technologies to be tested. A system of direct
pressure measurement was therefore required.

For dual wheel assemblies, it was also necessary that the technicians be
able to monitor temperature and pressure and adjust the pressure in both
wheels simultaneously. This functionally required a sophisticated
custom-designed slip ring assembly capable of passing air and data
signals from the rotating wheels to the non-rotating tractor-trailer
frame and up to the cab. The thermocouple data was read directly by the
DAS while the pressure lines were plumbed into a manifold to allow the
selection of the tire(s) to be monitored by the pressure transducers.
The use of the same lines to both monitor and adjust the tire pressures
required the test engineer to periodically close the exhaust valves when
making adjustments to tire pressures to check the pressure of the tire
being adjusted. This process, while somewhat inconvenient, minimized the
number of pressure lines on the vehicle.

The test team identified a manufacturer capable of supplying five of
these slip ring assemblies in a rugged package designed for the vehicle
environment, Dynamic Sealing Technologies Incorporated.[^12]

Exhibit 3.8 shows some photographs of the dual-flow rotary union and
slip ring assembly.

[]{#__RefHeading___Toc149980556 .anchor}Exhibit 3.8 -- Dual-Flow Rotary
Union and Slip Ring Assembly

![](media/image30.jpeg){width="6.5in" height="2.9229166666666666in"}

![](media/image31.png){width="3.25in"
height="2.5in"}![](media/image32.png){width="3.25in" height="2.5in"}

### Custom Pressure Control Manifold

The use of the slip ring assemblies required the design and assembly of
a cab-mounted pressure control manifold. The control manifold provided
the test engineer with the ability to regulate tire pressure by removing
and adding air within the tire and wheel assembly while the vehicle is
in motion. The control board also included the pressure transducers.

Exhibit 3.9 shows a schematic of the custom pressure control manifold,
while Exhibit 3.10 shows a photograph of the assembled manifold.

[]{#__RefHeading___Toc149980557 .anchor}Exhibit 3.9 -- Pressure Control
Manifold Schematic

![](media/image33.wmf){width="5.908333333333333in"
height="8.422916666666667in"}

[]{#__RefHeading___Toc149980558 .anchor}Exhibit 3.10 -- Pressure Control
Manifold and Metering Valve

![](media/image34.png){width="3.0833333333333335in"
height="4.0055555555555555in"}![](media/image35.png){width="2.1972222222222224in"
height="3.9805555555555556in"}

### Brake Reservoir and Treadle Valve Pressure Transducers

The failure modes test (Test #4) required that the air brake systems be
monitored to determine whether the central tire inflation systems
degraded the vehicle's potential braking ability (see Chapter 4 for test
matrix description). It was necessary to monitor the air brake system
pressure at three points---primary air reservoir, secondary air
reservoir, and application pressure. Three pressure transducers similar
to those used for tire pressure monitoring were spliced into the brake
lines at a tee in the following locations:

-   The primary air reservoir

-   The secondary air reservoir

-   The application pressure gauge line upstream of the gauge.

Output voltage levels from the transducers were then connected to the
data acquisition system.

### Digital Marker Switch

Many of the test procedures required recording when a warning indicator
activates/illuminates. Since many of these products tested were a closed
system design and could not be integrated with the DAS, a device was
needed to allow the test engineer to electronically mark/tag the DAS
data when a low-pressure warning was observed. This was accomplished by
placing a simple switch at the control manifold that placed a voltage
signal on a channel in the DAS when pressed. (See Exhibit 3.11 for a
photo of a digital marker switch.)

[]{#__RefHeading___Toc149980559 .anchor}Exhibit 3.11 -- Digital Marker
Switch Photo

![](media/image34.png){width="2.0708333333333333in"
height="2.5034722222222223in"}

### Non-Contact Fifth Wheel

A non-contact (optical) fifth wheel was installed on the tractor and
motorcoach to provide a reference vehicle speed. On both vehicles, the
fifth wheel was hard-mounted to the driver side of the vehicle just aft
of the driver's position.

### DAS

The sensor data was electronically processed by a DAS manufactured by
Link Engineering Company[^13] of Detroit, MI, as shown in Exhibit 3.12.
A PC-based laptop computer operates the system, stores data as it is
acquired, and performs real-time analyses. The system software supports
a variety of interface options ranging from direct user interaction with
the system during measurement to completely autonomous operation based
on various pre-programmed "trigger" events that cause the system to
begin data collection. The system is also capable of issuing prompts to
a test driver or an instrumentation technician.

[]{#__RefHeading___Toc149980560 .anchor}Exhibit 3.12 - Link DAS

![](media/image36.wmf)

The system is modular and, for this test program, was configured with
eight multi-channel signal-processing modules. See Exhibit 3.13 for
complete specifications.

[]{#__RefHeading___Toc149980561 .anchor}Exhibit 3.13 ‑ Links DAS
Specification

  ------------------------------------------ ----------------------------
  **Specification**                          

  Model Number                               2060

  Noise, Vibration and Harshness Channels    5-32

  Base Analog Channels                       8

  Maximum Additional Analog Channels         64

  Maximum Samples per Second:\               1,000\
  General Analog\                            51,200
  High-Speed NVH (Noise/Vibration/Harshness) 

  Temperature Channels                       8-64

  Thermocouple Type                          J or K

  Real-Time Data Display                     Yes

  Heads-up Driver Display                    Yes

  Review Data in Vehicle                     Yes

  Continuous Data Sampling                   Yes

  Real-Time Spectrum Analysis                25,000 Hz for 5 channels
                                             sampled simultaneously

  Typical System Dimensions                  11" wide x 8.5" deep x 5.5"
                                             high

  Power Requirements -- Volts                9 to 15

  Power Requirements -- Amps                 4 Max.
  ------------------------------------------ ----------------------------

The processing modules included three thermocouple modules, one pressure
module, one force module, one frequency counter module, one network
module, and the master module. The master module housed the power
supply, computer, and heads-up display ports. A memory cache within the
Link system stores one second of data before the beginning of the data
logging event.

The Link 2060 DAS was set up to record the following information for
each test:

-   Test tire pressures (and associated dual tire pressure where
    applicable)

-   Internal tire temperatures

-   Primary and secondary brake reservoir pressures

-   Treadle valve pressures

-   Vehicle speed

-   Warning indicator marker (manually triggered marker used to indicate
    in the data when a warning is displayed by the system).

In particular, 16 data channels were recorded, as shown in Exhibit 3.14.

[]{#__RefHeading___Toc149980562 .anchor}Exhibit 3.14 -- Sensor Channels

  ------------------------------------------------------------------------
  **Channel    **Description**                                Units
  \#**                                                        
  ------------ ---------------------------------------------- ------------
  1            Non Contact 5th Wheel Speed                    mph

  2            Pressure Transducer #1                         psi

  3            Pressure Transducer #2                         psi

  4            Primary Reservoir Pressure Transducer          psi

  5            Secondary Reservoir Pressure Transducer        psi

  6            Break Pedal Control Pressure Transducer        psi

  7            Temperature Right Front Steer Tire             degrees F

  8            Temperature Left Front Outer Drive Tire        degrees F

  9            Temperature Left Front Inner Drive Tire        degrees F

  10           Temperature Right Rear Inner Drive Tire        degrees F

  11           Temperature Right Rear Outer Drive Tire        degrees F

  12           Temperature Right Front Inner Trailer Tire     degrees F

  13           Temperature Right Front Outer Trailer Tire     degrees F

  14           Temperature Left Rear Outer Trailer Tire       degrees F

  15           Temperature Left Rear Inner Trailer Tire       degrees F

  16           Marker Switch                                  On/Off
  ------------------------------------------------------------------------

# TEST PLAN

Each one of the TPMS was installed sequentially, first on the
tractor-trailer and then on the motorcoach, and tested at loaded
conditions based on a pre-defined test plan. As each test series was
completed and the results analyzed, the test plan was modified by either
eliminating certain planned test sequences that were not expected to
generate new and useful data, or by adding tests to investigate specific
issues or new areas of interest. This section of the report describes
the:

-   Specific TPMS testing regimens performed under this program (the
    test matrix)

-   Processes used for collecting data

All track testing occurred at the TRC in East Liberty, OH, using TRC
drivers.

## Test Matrix

The test program consisted of the following seven specific tests, not
all of which were performed on each system or technology:

+--------------------------------+-------------------------------------+
| -   Test #1: Functionality     | -   Test #5: Disablement Test       |
|     Tests                      |                                     |
+--------------------------------+-------------------------------------+
| -   Test #2: Threshold Warning | -   Test #6: Operation Interface    |
|     Test                       |     Evaluation                      |
+--------------------------------+-------------------------------------+
| -   Test #3: Loaded Test at    | -   Test #7: Gate-Reader Evaluation |
|     High Speed                 |                                     |
+--------------------------------+-------------------------------------+
| -   Test #4: Failure Mode Test |                                     |
+--------------------------------+-------------------------------------+

Exhibit 4.1 shows an overview of the test matrix that maps each of the
systems tested to the specific tests above.

[]{#__RefHeading___Toc149980563 .anchor}Exhibit 4.1 -- Test Matrix

### Functionality Test (Static and Dynamic)

This is an overview or "shakedown" test phase that characterizes the
operational, maintenance, and installation processes for each system.

The major objective of this test phase was to evaluate the overall
ability of the various sensor technologies to detect tire pressure
problems or otherwise perform as intended.

### Threshold Warning Level Test

This test determines the thresholds at which low tire pressure warnings
are given. In the case of the automatic inflation systems, the test
determines the leak rate (psi/min) in which the inflation system can no
longer keep pace and a low tire pressure warning is given.

### Loaded Test at High Speed

This test examines the effects of tire heating, due to sustained
high-speed driving, on the warning indicator/light of the systems.

### Failure Modes Test

This test phase determines whether, for automatic inflation systems, a
large or catastrophic air leak depletes the air supply for the pneumatic
brakes or forces the system to run continuously without giving the
driver a warning that a tire has lost air. For systems where tires are
interconnected (dual-tire equalizing and central inflation system
technologies), the purpose is to ensure that loss of inflation pressure
in a single tire does not affect the interconnected tires.

### Disablement Test

This test determines the system's ability to provide a warning or some
type of indication if/when it is disabled either by an intentional act
or as a result of a failure of a system or component. At least five
modes, in which each system could be disabled, were tested.

### Operator Interface Evaluation

This test is a qualitative evaluation of the effectiveness of the driver
interface.

### Gate Reader Evaluation

This test evaluates the performance and reliability of the drive-thru
gate readers used with tire-mounted monitoring systems. The objective
was to determine the speed and consistency of the gate readers in
capturing pressures of all 18 tires.

## Data Collection Process

The Link DAS system received information from 16 individual channels at
a frequency of 10 Hz. Exhibit 3.13 provides a complete list of channels.
A key stroke on the laptop activated the DAS at the beginning of each
test run. Data was collected until the vehicle reached a complete stop.
A memory cache built into the DAS recorded one second of data prior to
the start of data recording.

The actual data from each test run was stored in individual files on a
Windows-based laptop computer installed in each test vehicle in turn.
The average TPMS test lasted about 10 to 30 minutes and generated
approximately 5,000 to 10,000 data points. In total, the testing program
generated approximately 450 Mb of data.

The test engineer was responsible for manually recording the test
identification number and other specific information including
environmental conditions and tire(s) under test, as well as any specific
warnings or indications by the TPMS. This was necessary because the TPMS
are all self-contained and were not connected directly to the Link DAS
because they did not have signal outputs that could be tapped for direct
recording.

[]{.mark}

[]{.mark}

# TEST RESULTS

This chapter presents a summary of the results from the test program and
offers some observations regarding the accuracy, sensitivity, and
applicability of various TPMS technologies for determining tire pressure
deficiencies.

Due to the very large volume of data generated (450 Mb), it is not
practical to plot data from all test runs and/or perform comprehensive
comparisons among all TPMS for all test scenarios in this report.
Therefore, this chapter presents analyses performed to assess the
operational characteristics and limitations of the various TPMS
technologies.

The project team developed a test plan to address the various
performance parameters of the TPMS technologies, which was reviewed by
the project sponsor, TRC engineers and, where appropriate, by TPMS
vendors. The initial test plans followed proposed test procedures. The
final test plans produced a test matrix that more efficiently utilized
track time and incorporated modifications to the test procedures related
to characteristics of the selected TPMS technologies.

The results and observations presented in this chapter are not
exhaustive; however, extensive data was collected and supports
significant additional statistical analyses. Other tire researchers may
wish to examine the data and draw independent conclusions on TPMS
performance and the utility of the various systems examined in this
program.[^14]

This chapter is organized as follows:

-   An analysis of the data collected from the dual tire equalizers

-   An analysis of the data collected from the tire pressure monitoring
    systems

-   An analysis of the data collected from the central tire inflation
    systems

## Dual Tire Equalizers

The following tests were performed on the dual tire equalizers:

-   Static and dynamic functionality tests

-   Threshold warning tests

-   Failure modes tests

-   Disablement modes tests

-   Operator interface evaluation

These tests and the test results are described in detail in the
following subsections.

### Static and Dynamic Functionality Tests

The static and dynamic functionality tests assess the ability of tire
equalizers to equalize between tires of a dual installation as well as
to isolate a good tire from a tire that has experienced a significant or
total loss of pressure. The systems were tested both statically to
determine basic functionality and dynamically to determine the effect of
the vehicle operation on the equalizer system's performance.

Exhibit 5.1 summarizes the dual tire equalizer functionality test
procedure. Although equalizers can be installed on motorcoaches and
trucks, the two equalizer systems were tested on the tractor-trailer
because the larger number of dual wheel installations on the vehicle
facilitated and improved efficiency of the testing.

[]{#__RefHeading___Toc149980564 .anchor}Exhibit 5.1 -- Dual Tire
Equalizer Functionality Test Procedures

  --------------- ---------------------------------------------------------------
  **Step Number** **Procedure**

  Static          
  Functionality   
  Check           

  1               Set all tires to Cold Inflation Pressure (CIP=100 psi), Create
                  new test file

  2               Set Manifold to Proper Positions

  3               Start Data Recorder, sample at 10 Hz

  4               Deflate RROD tire to 85 psi, using manifold

  5               Stop recorder when pressures have equalized for at least 1
                  minute or up to 10 minutes have elapsed.

  6               Record file name and stop number

  7               Examine display at wheel, Take digital photo, Record Photo File
                  Name

  8               Re-inflate \"giving\" tire to 100 psi, Deflate RROD additional
                  10 psi below previous setting

  9               Repeat 1-8 until pressure reaches 55 psi or tires no longer
                  equalize pressures

  10              Repeat 1-9 for LFID, and RFIT and LROT

  Dynamic         
  Functionality   
  Check           

  11              Set all tires to Cold Inflation Pressure (CIP=100psi), Create
                  new test file

  12              Set Manifold to Proper Positions

  13              Start Data Recorder, sample at 10 Hz

  14              Deflate RROD tire to 85 psi, using manifold

  15              Drive vehicle at 45 mph for 10 minutes (1 lap), stop vehicle in
                  pit

  16              Stop Data Recorder

  17              Record file name and stop number

  18              Examine display at wheel, Take digital photo. Record Photo File
                  Name

  19              Re-inflate \"giving\" tire to 100 psi, Deflate RROD additional
                  10 psi below previous setting

  20              Repeat 11-19 until pressure reaches 55 psi or tires no longer
                  equalize pressures

  21              Repeat 11-20 for LFID, RFIT, and LROT
  --------------- ---------------------------------------------------------------

Exhibit 5.2 shows the Link equalizer equalizing a dual installation
during a static test in which the left front inner drive (LFID) tire's
pressure was dropped to 75 psi and the corresponding left front outer
drive (LFOD) tire was set at 100 psi. The low pressure and spikes in the
LFID trace are due to the high rate of deflation and intermittent
checking of the pressure by the test engineer during the deliberate
reduction to 75 psi. Due to the location of the transducer relative to
the position of the exhaust valve used to deflate the tire, the pressure
reads lower than actual tire pressure during high deflation rates. The
exhaust valve must be closed intermittently during deflation to check
the pressure in the tire being deflated. The tires begin to equalize
immediately on the reduction of pressure as evidenced by the LFOD trace.
The data show that the tires equalized at approximately 81 psi. The
temperatures of both tires also show a decrease as their pressures
dropped (as would be expected). The spike in the marker trace indicates
the point where the LFID reached the 75 psi test point.

[]{#__RefHeading___Toc149980565 .anchor}Exhibit 5.2 -- Link Equalizer
Static Equalizer Functionality Test LFID 75 psi

![](media/image37.wmf){width="6.566666666666666in"
height="4.036111111111111in"}

Exhibit 5.3 shows the Link equalizer equalizing a dual installation
during a static test in which the LFID tire's pressure was dropped to 55
psi and the corresponding LFOD tire was set at

100 psi. The low pressure and spikes in the LFID trace are due to the
high exhaust rate and intermittent checking of the pressure by the test
engineer during the deliberate reduction to

55 psi. The tires begin to equalize immediately on the reduction of
pressure as evidenced by the LFOD trace. The data show that the tires do
not equalize but remain isolated by the check valve in the system. The
LFID remains at approximately 58 psi and the LFOD remains at
approximately 80 psi. The temperatures of both tires again decrease as
their pressures drop. The spike in the marker trace indicates the point
where the LFID reached the 55 psi test point.

[]{#__RefHeading___Toc149980566 .anchor}Exhibit 5.3 -- Link Equalizer
Static Equalizer Functionality Test LFID 55 psi

![](media/image38.wmf){width="6.566666666666666in"
height="3.990972222222222in"}

Exhibit 5.4 summarizes the data from the Link equalizer static
functionality testing. The system appears to equalize the pressure of
the tire experiencing air loss until it decreases to approximately 80
psi. When a leaking tire deflates below 80 psi, the system will stop
pressure equalization when the pressure of the intact tire reaches 80
psi to prevent the total loss of pressure in both tires of a dual
installation.

[]{#__RefHeading___Toc149980567 .anchor}Exhibit 5.4 -- Link Equalizer
Static Functionality Test Data

  ------------- ---------------- --------------------- -------------------
  **Tire Set**  **Initial        **Equalized           **Isolated
                Pressure**       Pressures**           Pressures**

  RROD/RRID     85/100           90/90                 \-

                75/100           82/82                 \-

                65/100           79/79                 \-

                55/100           \-                    74/80

  LFID/LFOD     85/100           90/90                 \-

                75/100           82/82                 \-

                65/100           \-                    70/78

                55/100           \-                    58/80

  RFIT/RFOT     85/100           86/86                 \-

                75/100           78/78                 \-

                65/100           \-                    66/80

                55/100           \-                    55/80

  LROT/LRIT     85/100           89/89                 \-

                75/100           85/85                 \-

                65/100           79/79                 \-

                55/100           \-                    62/82
  ------------- ---------------- --------------------- -------------------

Exhibit 5.5 summarizes the data from the V-Tech equalizer static
functionality testing. Similar to the Link equalizer, the system appears
to equalize pressures down to slightly below 80 psi. However, the
equalizer on the LFID/LFOD tire set did show a tendency to isolate the
intact tire at pressures in the mid 90 psi range when presented with a
larger pressure differential. Similar to the Equalizer System #1, when a
tire deflates below 80 psi, the system will stop pressure equalization
from the intact tire 80 psi to prevent the loss of pressure in both
tires of a dual installation.

[]{#__RefHeading___Toc149980568 .anchor}Exhibit 5.5 -- V-Tech Equalizer
Static Functionality Test Data

  ------------- ---------------- --------------------- -------------------
  **Tire Set**  **Initial        **Equalized           **Isolated
                Pressure**       Pressures**           Pressures**

  RROD/RRID     95/100           98/98                 \-

                90/100           95/95                 \-

                85/100           92/92                 \-

                80/100           89/89                 \-

                75/100           86/86                 \-

                70/100           85/85                 \-

                65/100           79/79                 \-

                60/100           78/78                 \-

                55/100           \-                    74/79

  LFID/LFOD     85/100           92/92                 \-

                75/100           86/86                 \-

                65/100           \-                    77/84

                55/100           \-                    56/96

  RFIT/RFOT     85/100           92/92                 \-

                75/100           86/86                 \-

                65/100           78/78                 \-

                55/100           \-                    71/75

  LROT/LRIT     85/100           93/93                 \-

                75/100           85/85                 \-

                65/100           79/79                 \-

                55/100           \-                    62/82
  ------------- ---------------- --------------------- -------------------

Exhibit 5.6 shows the V-Tech equalizer equalizing a dual installation,
during a dynamic test at 45 mph. During this test, the LFID tire's
pressure was dropped to 85 psi while the corresponding LFOD tire was
initialized at 100 psi. The low pressure and spikes in the LFID trace
are due to the high exhaust rate and intermittent checking of the tire
pressure during the deliberate reduction to 85 psi. The tires begin to
equalize immediately on the reduction of pressure as evidenced by the
LFOD trace. The data show that the tires equalized at approximately 92
psi. This result was similar to the equalization pressure in the static
functionality test. The temperatures of both tires also show an initial
decrease as their pressures dropped and then an increase as the vehicle
was driven at a constant speed of 45 mph. This is indicated by the spike
in the marker trace.

[]{#__RefHeading___Toc149980569 .anchor}Exhibit 5.6 -- V-Tech Equalizer
Dynamic Equalizer Functionality Test LFID 85 psi

![](media/image39.wmf){width="6.566666666666666in" height="4.06875in"}

Exhibit 5.7 shows the V-Tech equalizer equalizing a dual installation
during a dynamic test at 45 mph. In this test, the LFID tire's pressure
was deliberately reduced to 55 psi and the corresponding LFOD tire was
initially set at 100 psi. Similar to the results shown in Exhibit 5.3,
the low pressure and spikes in the LFID trace are due to the high
exhaust rate and intermittent checking of the tire pressure by the test
engineer during the deliberate reduction to 55 psi. The tires begin to
equalize immediately when the reduction of pressure was detected, as
shown by the LFOD trace. The data trace indicates that the pressures
between the dual tires do not equalize, but that they remain isolated by
the check valve in the system. The LFID pressure was increased to
approximately 55 psi at the beginning of the equalization period and
increased gradually to 56 psi. The LFOD dropped to approximately 96 psi
at the beginning of the equalization sequence and gradually increased to
approximately 97 psi. The isolation pressures were similar to the
pressures observed in the static functionality tests for this case. The
temperatures of both tires initially decrease as their pressures drop,
but begin to increase as the vehicle is driven. The slight increase in
pressure after the start of the test, as indicated by the spike in the
marker trace, is due to the temperature increase in the tires as the
vehicle is driven.

[]{#__RefHeading___Toc149980570 .anchor}Exhibit 5.7 -- V-Tech Equalizer
Dynamic Equalizer Functionality Test LFID 55 psi

![](media/image40.wmf){width="6.566666666666666in"
height="4.016666666666667in"}

Exhibit 5.8 summarizes the data from the Link equalizer dynamic
functionality testing. Similar to its static test behavior, the system
appears to equalize pressures down to approximately 80 psi. However, the
equalizers on the RROD/RRID and LROT/LRIT tire sets isolated the intact
tires at pressures just below 90 psi when the low tire's pressure set to
65 psi and 75 psi respectively. Again as in the static tests, when a
tire deflates below approximately 80 psi, the system will halt pressure
equalization from the intact tire at approximately 80 psi to prevent the
loss of pressure in both tires of a dual installation.

[]{#__RefHeading___Toc149980571 .anchor}Exhibit 5.8 -- Link Equalizer
Dynamic Functionality Test Data

  ------------- ---------------- --------------------- -------------------
  **Tire Set**  **Initial        **Equalized           **Isolated
                Pressure**       Pressures**           Pressures**

  RROD/RRID     85/100           91/91                 \-

                75/100           82/82                 \-

                65/100           \-                    66/88

                55/100           \-                    71/80

  LFID/LFOD     85/100           90/90                 \-

                75/100           81/81                 \-

                65/100           \-                    70/78

                55/100           \-                    58/80

  RFIT/RFOT     85/100           89/89                 \-

                75/100           80/80                 \-

                65/100           \-                    69/79

                55/100           \-                    59/82

  LROT/LRIT     85/100           89/89                 \-

                75/100           \-                    76/89

                65/100           80/80                 \-

                55/100           \-                    63/83
  ------------- ---------------- --------------------- -------------------

Exhibit 5.9 summarizes the data from the V-Tech equalizer dynamic
functionality testing. Similar to its static test behavior, the system
appears to equalize pressures down to approximately 80 psi. However, the
equalizers on the LFID/LFOD tire set isolated the intact tires at 96 psi
when the other tire dropped to 55 psi.

[]{#__RefHeading___Toc149980572 .anchor}Exhibit 5.9 -- V-Tech Equalizer
Dynamic Functionality Test Data

  ------------- ---------------- --------------------- -------------------
  **Tire Set**  **Initial        **Equalized           **Isolated
                Pressure**       Pressures**           Pressures**

  RROD/RRID     95/100           97/97                 \-

                90/100           95/95                 \-

                85/100           92/92                 \-

                80/100           89/89                 \-

                75/100           86/86                 \-

                70/100           85/85                 \-

                65/100           79/79                 \-

                60/100           78/78                 \-

                55/100           \-                    74/79

  LFID/LFOD     85/100           92/92                 \-

                75/100           86/86                 \-

                65/100           \-                    78/84

                55/100           \-                    56/96

  RFIT/RFOT     85/100           92/92                 \-

                75/100           85/85                 \-

                65/100           82/82                 \-

                55/100           \-                    69/75

  LROT/LRIT     85/100           93/93                 \-

                75/100           86/86                 \-

                65/100           80/80                 \-

                55/100           \-                    63/83
  ------------- ---------------- --------------------- -------------------

### Threshold Warning Tests

The threshold warning tests evaluate the ability of tire equalizers to
equalize inflation pressures between the two tires of a dual
installation at slow leak rates, as well as to isolate an intact tire
from a tire that has experienced a slow leak that results in a total
loss of pressure. The systems were tested both statically to determine
basic functionality and dynamically to determine the effect of the
vehicle operation on the equalizer system's performance. Exhibit 5.10
presents the dual tire equalizer threshold warning test procedures.

[]{#__RefHeading___Toc149980573 .anchor}Exhibit 5.10 -- Dual Tire
Equalizer Threshold Warning Test Procedures

  -------------------------------------------------------------------------------
  **Step Number** **Procedure**
  --------------- ---------------------------------------------------------------
  Static Slow     
  Leak            

  1               Set all tires to Cold Inflation Pressure (CIP=100 psi), Create
                  new test file

  2               Start Data Recorder, sample at 10 Hz

  3               Begin slowly leaking RROD tire pressure at approximately 1.5
                  psi/min\*

  4               Allow tire to deflate until pressure reaches 60 psi, stop
                  deflation

  5               Stop Data Recorder

  6               Record file name and stop number

  7               Repeat 1-6 for LFID, and RFIT and LROT

  Dynamic Slow    
  Leak            

  8               Start Data Recorder, sample at 10 Hz

  9               Begin slowly leaking LROT tire pressure at approximately 1.5
                  psi/min\*

  10              Drive vehicle at 45 mph, until LROT tire pressure reaches 60
                  psi, or two hours have elapsed.

  11              Stop Data Recorder, Stop Leak

  12              Record file name and stop number

  \*Do not exceed 
  40% below CIP   
  for             
  drive/trailer   
  tires, or 25%   
  below CIP for   
  steer tires     
  -------------------------------------------------------------------------------

Exhibit 5.11 shows the Link equalizer equalizing a pair of duals during
a static test. During this test, the LRIT tire's pressure slowly dropped
due to an induced leak of approximately 1.5 psi per minute and the
corresponding LROT tire was set at 100 psi. The tires begin to equalize
immediately on the reduction of pressure as shown by both the LRIT and
LROT traces. The LROT tire stabilized at approximately 78 psi, while the
LRIT tire continued to deflate at a slightly higher rate because the
check valve activated and discontinued the equalization process. The
temperatures of both tires remained relatively constant during the slow
leak process.

[]{#__RefHeading___Toc149980574 .anchor}Exhibit 5.11 -- Link Equalizer
Static Slow Leak Test

![](media/image41.wmf){width="6.566666666666666in"
height="3.984027777777778in"}

Exhibit 5.12 shows the Link equalizer equalizing a dual installation
during a dynamic test at

45 mph. Here, the LRIT tire's pressure slowly dropped due to an induced
leak of approximately 1.5 psi per minute, while the corresponding
initial LROT was set at 100 psi. The tires begin to equalize immediately
on the reduction of pressure as evidenced by both the LRIT and LROT
traces. The data show that the LROT tire stabilized at approximately 75
psi, while the LRIT tire continued to deflate at a slightly faster rate.
As in the previous test, the check valve activated and discontinued the
equalization process. The temperatures of both tires gradually increased
during the slow leak process due to the heating induced by driving the
vehicles.

[]{#__RefHeading___Toc149980575 .anchor}Exhibit 5.12 -- Link Equalizer
Dynamic Slow Leak Test

![](media/image42.wmf){width="6.566666666666666in"
height="4.016666666666667in"}

Exhibit 5.13 summarizes the data from the Link equalizer threshold
warning testing. During the static and dynamic testing with a slowly
leaking tire, the system appears to equalize pressures down to
approximately 80 psi, although the pressures of the isolated tires were
in the mid to upper 70 psi range. Because the air loss rates were low,
the equalizers on the RROD/RRID and LFID/LFOD equalized but did not
isolate the intact tire of the dual pair during the test period.

[]{#__RefHeading___Toc149980576 .anchor}Exhibit 5.13 -- Link Equalizer
Threshold Warning Test Data

  ----------------- ----------------- ----------------- -----------------
  **Tire Set**      **Initial         **Equalized       **Isolated
                    Pressures**       Pressures**       Pressures**

  Static                                                

  RROD/RRID         100/100           87/87             Test Period
                                                        Expired

  LFID/LFOD         100/100           75/75             Test Period
                                                        Expired

  RFIT/RFOT         100/100           \-                Continued Leak/79

  LROT/LRIT         100/100           \-                Continued Leak/78

  Dynamic                                               

  RROD/RRID         100/100           \-                Continued Leak/74
  ----------------- ----------------- ----------------- -----------------

Exhibit 5-14 summarizes the data from the V-Tech equalizer threshold
warning testing. During the static and dynamic testing with a slowly
leaking tire, the system appears to equalize pressures down to
approximately 80 psi. Similar to the Link equalizer, the pressures of
the isolated tires were also in the mid to upper 70 psi range.

[]{#__RefHeading___Toc149980577 .anchor}Exhibit 5.14 -- V-Tech Equalizer
Threshold Warning Test Data

  ----------------- ----------------- ----------------- -----------------
  **Tire Set**      **Initial         **Equalized       **Isolated
                    Pressures**       Pressures**       Pressures**

  Static                                                

  RROD/RRID         100/100           \-                Continued Leak/78

  LFID/LFOD         100/100           \-                Continued Leak/78

  RFIT/RFOT         100/100           \-                Continued Leak/73

  LROT/LRIT         100/100           \-                Continued Leak/74

  Dynamic                                               

  LROT/LRIT         100/100           \-                Continued Leak/74
  ----------------- ----------------- ----------------- -----------------

### Failure Modes Tests

The failure modes tests for tire equalizers evaluate their ability to
equalize between two tires of a dual installation at rapid leak rates as
well as to isolate an intact tire from a tire that has experienced a
rapid leak that results in total loss of pressure. The systems were
tested both statically to determine basic functionality and dynamically
to determine the effect of the vehicle operation on the equalizer
system's performance. Exhibit 5.15 details the dual tire equalizer
failure modes test procedures.

[]{#__RefHeading___Toc149980578 .anchor}Exhibit 5.15 -- Dual Tire
Equalizer Failure Modes Test Procedures

  --------------- ---------------------------------------------------------------
  **Step Number** **Procedure**

  Static Rapid    
  Leak            

  1               Set all tires to Cold Inflation Pressure (CIP=100 psi), Create
                  new test file

  2               Start Data Recorder, sample at 10 Hz

  3               Initiate air loss from RROD tire at the maximum rate
                  (approximately 20 psi/min.)

  4               Wait until pressure in RROD reaches 0 psi and RRID pressure
                  stabilizes for 1 minute

  5               Stop Data Recorder

  6               Record file name and stop number

  Dynamic Rapid   
  Leak            

  7               Set all tires to Cold Inflation Pressure (CIP=100 psi), Create
                  new test file

  8               Start Data Recorder, sample at 10Hz

  9               Initiate air loss from RROD tire at maximum rate (approximately
                  20 psi/min.)

  10              Drive vehicle at 45 mph, until RROD tire pressure reaches 60
                  psi

  11              Stop Data Recorder, Stop air loss

  12              Record file name and stop number

  \*Do not exceed 
  40% below CIP   
  for             
  drive/trailer   
  tires, or 25%   
  below CIP for   
  steer tires     
  --------------- ---------------------------------------------------------------

Exhibit 5.16 shows the V-Tech equalizer equalizing a dual installation
during a static test in which the LFID tire's pressure rapidly dropped
due to an induced leak of 20 psi per minute. Both the LFID and
corresponding LFOD tires were initially set at 100 psi. The tires begin
to equalize immediately on the reduction of pressure as evidenced by
both the LFID and LFOD traces. The data show that the LFOD tire
stabilized at approximately 95 psi, while the LFID tire continued to
deflate at a slightly faster rate because the check valve activated and
discontinued the equalization process. The temperatures of the LFID tire
initially dropped due to the decrease in pressure, while the temperature
of the LFOD tire remained relatively constant. The large initial drop
and relatively low pressure of the LFID trace is due to the effect of
the large induced leak on the pressure transducer installation.

[]{#__RefHeading___Toc149980579 .anchor}Exhibit 5.16 -- V-Tech Equalizer
Static Rapid Leak LFID Test

![](media/image43.wmf){width="6.566666666666666in" height="4.06875in"}

Exhibit 5.17 shows the performance of the V-Tech equalizer on a dual
installation during a dynamic test at 45 mph where the LFID tire's
pressure rapidly dropped due to an induced leak of approximately 20 psi
per minute. Both the LFID and the corresponding LFOD tires were
initially set at 100 psi. The tires begin to equalize immediately on the
reduction of pressure as evidenced by the LFOD trace. The data show that
the LFOD tire stabilized at approximately 95 psi, while the LFID tire
continued to deflate until testing was terminated when the LFID tire
reached 60 psi. The temperatures of both tires initially dropped due to
the decrease in pressure and then gradually increased due to heat
generated from driving the vehicle. As mentioned previously, the large
initial drop and relatively low pressure of the LFID trace is due to the
effect of the high induced leak rate on the pressure transducer
installation, while the spikes are due to intermittent checks of the
tire pressure.

[]{#__RefHeading___Toc149980580 .anchor}Exhibit 5.17 -- V-Tech Equalizer
Dynamic Rapid Leak LFID Test

![](media/image44.wmf){width="6.566666666666666in"
height="4.022916666666666in"}

Exhibit 5.18 summarizes the data from the Link equalizer failure mode
testing. During the static and dynamic testing with a rapidly leaking
tire, the system appears to equalize pressures down to approximately 80
psi in the LFID/LFOD and RFIT/RFOT tire pairs. The RROD/RRID and
LROT/LRIT pairs, however, stopped equalizing when the pressures of the
isolated tires were in the high-80s psi range.

[]{#__RefHeading___Toc149980581 .anchor}Exhibit 5.18 -- Link Equalizer
Failure Mode Test Data

  ------------------- -------------------- ------------------------------
  **Tire Set**        **Initial Pressures  **Isolated Pressures (psi)**
                      (psi)**              

  Static                                   

  RROD/RRID           100/100              Continuing Leak/88

  LFID/LFOD           100/100              Continuing Leak/80

  RFIT/RFOT           100/100              Continuing Leak/80

  LROT/LRIT           100/100              Continuing Leak/89

  Dynamic                                  

  RROD/RRID           100/100              Continuing Leak/89

  LFID/LFOD           100/100              Continuing Leak/78

  RFIT/RFOT           100/100              Continuing Leak/80

  LROT/LRIT           100/100              Continuing Leak/88
  ------------------- -------------------- ------------------------------

Exhibit 5.19 summarizes the data from the V-Tech equalizer failure mode
testing. During the static testing of a rapidly leaking tire in a pair,
the system appears to equalize pressures down to a range of 88 to 95
psi. During dynamic testing of a rapidly leaking tire in a pair, the
system appears to equalize pressures down to a range of 90 to 95 psi.
Safety requirements prevented continuing the dynamic testing beyond the
point where the pressure of an affected tire went below 60 psi. Thus, we
were not able to test the equalization pressures when the affected tire
was isolated in the RROD/RRID, RFIT/RFOT, and LROT/LRIT tests. The
LFID/LFOD tire set did reach the isolation point of 95 psi during both
the dynamic and static tests.

[]{#__RefHeading___Toc149980582 .anchor}Exhibit 5.19 -- V-Tech Equalizer
Failure Mode Test Data

  ------------------- -------------------- ------------------------------
  **Tire Set**        **Initial Pressures  **Isolated Pressures (psi)**
                      (psi)**              

  Static                                   

  RROD/RRID           100/100              Continuing Leak/92

  LFID/LFOD           100/100              Continuing Leak/95

  RFIT/RFOT           100/100              Continuing Leak/88

  LROT/LRIT           100/100              Continuing Leak/88

  Dynamic                                  

  RROD/RRID           100/100              60/95 (Test Terminated at 60
                                           psi)

  LFID/LFOD           100/100              Continuing Leak/95

  RFIT/RFOT           100/100              60/90 (Test Terminated at 60
                                           psi)

  LROT/LRIT           100/100              60/90 (Test Terminated at 60
                                           psi)
  ------------------- -------------------- ------------------------------

### Disablement Tests

The purpose of this test is to determine the ability of the system to
protect the tire(s) from loss of air pressure in the event of damage or
failure of the system components. Components of the system were
purposely damaged or removed to simulate damage or loss due to road
debris, curb strikes, vandalism, etc. These tests were performed
statically due to concerns about driver, vehicle, and track safety if a
tire failed on a moving vehicle. Exhibit 5.20 presents the test
procedures for the dual tire equalizer failure modes.

[]{#__RefHeading___Toc149980583 .anchor}Exhibit 5.20 -- Dual Tire
Equalizer Failure Modes Test Procedures

  ------------- ---------------------------------------------------------------
  **Step        **Procedure**
  Number**      

  Disablement   

  1             Set all tires to Cold Inflation Pressure (CIP=100 psi), Create
                new test file

  2             Start Data Recorder, sample at 10 Hz

  3             Disable the TPMS according to disablement Mode #1

  4             Examine display at wheel, Take digital photo, Record Photo File
                Name

  5             Record response of system & if/when a warning/indicator of
                disablement is observed

  6             Wait until response has stabilized for 1 minute

  7             Stop Data Recorder

  8             Record file name and stop number

  9             Examine display at wheel, Take digital photo, Record Photo File
                Name

  10            Repeat 1-9 for each mode of disablement

  Possible      
  Modes of      
  Disablement   

  1             Unscrew equalizer hose from RROD equalizer housing

  2             Unscrew equalizer hose from RROD valve

  3             Fracture sight glass on RROD equalizer housing

  4             Cut hose between valve and RROD stem
  ------------- ---------------------------------------------------------------

As summarized in Exhibit 5.21, the two TPMS tested responded somewhat
differently to the four disablement modes, but both isolated the good
tire from the tire with the induced failures.

[]{#__RefHeading___Toc149980584 .anchor}Exhibit 5.21 -- Dual Tire
Equalizer Failure Modes Test Data

  ----------------------- --------------------- --------------------------
  **Disablement Mode**    **Initial Tire        **Disablement Tire
                          Pressure (psi)        Pressure (psi) RROD/RRID**
                          RROD/RRID**           

  Link Equalizer                                

  Mode 1                  100/100               0/100

  Mode 2                  100/100               100/100

  Mode 3                  100/100               100/100

  Mode 4                  100/100               0/100

  V-Tech Equalizer                              

  Mode 1                  100/100               100/100

  Mode 2                  100/100               100/100

  Mode 3                  100/100               0/100

  Mode 4                  100/100               0/90
  ----------------------- --------------------- --------------------------

Mode 1 tested the responses of the systems to a hose unscrewing from the
equalizer block. For the Link equalizer, this resulted in the total loss
of air from the affected tire while the system isolated the intact tire
(similar to the previously discussed leak tests). For the V-Tech
equalizer, which uses a check valve on the equalizer block, the check
valve actuated and no air was lost from either tire.

Mode 2 tested the check valve in the tire valve and the check valve in
the equalizer block. During Mode 2 tests, both systems' check valves
actuated in the equalizer block, and the tire valves held the "fault"
tire at 100 psi. There was no loss of pressure from either tire in the
Link or V-Tech equalizers. The systems isolated the tire on the intact
side at 100 psi, and the tire valve held the "fault" tire at 100 psi.

Mode 3 tested the responses of the systems to a fractured cover glass on
the visual indicator. The two systems reacted differently in this
failure mode. For the Link equalizer, there was no leakage from either
tire. However, the V-Tech equalizer behaved as if there was a tire
failure resulting in loss of tire pressure in the RROD, and isolated the
RRID tire.

Mode 4 essentially tested the reactions of the systems to a catastrophic
tire failure by cutting the hose between the equalizer block and the
tire valve. Both systems responded with the check valve in the equalizer
block activating and isolating the side with the intact tire (or, in
this case, the intact valve) from the tire with the cut hose as its
pressure dropped to 0 psi.

### Operator Interface Evaluation

The pressure gauge for the Link equalizer is a yellow-and-black display
on the air valve. When the display is all yellow, it indicates the tire
pressure is within +/- 2 percent of the target inflation pressure.
Exhibit 5.22 displays the range of motion of the gauge. As pressure
drops, a vertical black line appears in the center of the display. The
bright yellow eye opens gradually as pressure drops, and the display
becomes completely black if dual tire pressure drops approximately 10
psi below the specified level. The technicians and drivers at TRC stated
that the yellow indicator gauge was easy to see during the walk-around
inspection and gave a positive indication of the tire pressures.

[]{#__RefHeading___Toc149980585 .anchor}Exhibit 5.22 -- Link Equalizer
Pressure Gauge

![](media/image45.jpeg){width="3.6145833333333335in"
height="3.0118055555555556in"}

Exhibit 5.23 displays the V-Tech equalizer gauge, which consists of a
pin that moves within a hole in the equalizer block. The tire pressure
is in the target range when the pin is flush with the surface of the
hole. The pin retracting into the hole indicated a pressure problem. TRC
drivers and technicians stated that, while the gauge did provide a
positive indication of the tire pressure condition, it could be
difficult at times to observe the pin position due to the small size and
limited travel of the pin.

[]{#__RefHeading___Toc149980586 .anchor}Exhibit 5.23 -- V-Tech Equalizer
Pressure Gauge

![](media/image46.jpeg){width="2.0819444444444444in"
height="1.3944444444444444in"}
![](media/image47.jpeg){width="2.0819444444444444in"
height="1.3944444444444444in"}

## Tire Pressure Monitoring Systems

Three types of tire pressure monitoring systems were evaluated:

-   **Valve-Stem-Mounted Tire Pressure Monitors,** connected to the
    exterior of the tire at the valve stem

-   **Wheel-Mounted Tire Pressure Monitors,** connected to the wheel,
    internal to the tire, typically using a metal band-strap

-   **Tire-Mounted Tire Pressure Monitors,** connected to the tire
    itself, either molded into place or using a mounting similar to a
    tire patch

These systems use devices mounted on the wheel or tire that monitor the
tire pressure and transmit an RF signal to a console containing a
receiver and display, which is located in the tractor cab or is readable
by an external handheld or drive-by gate reader.

Many systems also monitor temperature and convert the actual hot tire
pressure to cold pressure so that meaningful data is related to the
user. This temperature monitoring also has the added benefit of
compensating for tire temperature increases due to sustained
driving---thus, theoretically maintaining a low-pressure warning even as
the pressure increases in the tire due to excess heat buildup.

### Functionality Test

To understand how the TPMS technologies respond to slow air leaks, both
static and dynamic functionality tests were performed. These tests
involved initiating a slow leak (approximately a 1.5 psi/min initial
leak rate) in a test tire while monitoring the inflation pressure
through the DAS and recording warnings from the TPMS. This test was
performed both statically (vehicle not in motion) and dynamically (at 45
mph around the high-speed test track). The test procedure in Exhibit
5.24 was used to perform this test of the TPMS.

[]{#__RefHeading___Toc149980587 .anchor}Exhibit 5.24 -- TPMS
Functionality Test Procedures

  ---------- ---------------------------------------------------------------
  **Step     **Procedure**
  Number**   

  Static     

  1          Set all tires to Cold Inflation Pressure (CIP=100 psi), Create
             new test data file

  2          Set manifold to proper positions

  3          Start Data Recorder, Sample at 10 Hz

  4          Record Starting Tire Temperatures

  5          Begin Slowly reducing RFS tire pressure at approximately 1.5
             psi/min; do not exceed 40% below CIP for drive/trailer tires,
             or 25% below CIP for steer tires

  6          Press marker switch when system indicates low tire pressure
             (for those systems which have multiple warning levels, mark
             when each level is met)

  7          Stop Data Recorder

  8          Record file name and stop number

  9          Repeat 1-8 for LFID, RROD, RFIT, and LROT

  Dynamic    

  10         Set all tires to Cold Inflation Pressure (CIP=100psi), Create
             new test data file

  11         Set manifold to proper positions

  12         Start Data Recorder, Sample at 10 Hz

  13         Record Starting Tire Temperatures

  14         Begin Slowly reducing RFS tire pressure at approximately 1.5
             psi/min

  15         Drive vehicle at 45 mph until RFS reaches 40% below CIP for
             drive/trailer tires or 25% below CIP for steer tires or 2 hours
             have elapsed if those pressures are not reached.

  16         Press marker switch when system indicates low tire pressure
             (for those systems which have multiple warning levels, mark
             when each level is met)

  17         Stop Data Recorder

  18         Record file name and stop number

  19         Wait 30 minutes, or until tires return to temperatures recorded
             in Step 13

  20         Repeat 10-19 for LFID, RROD, RFIT, and LROT
  ---------- ---------------------------------------------------------------

Exhibit 5.25 shows the results of the static functionality tests on a
valve-stem-mounted TPMS.

[]{#__RefHeading___Toc149980588 .anchor}Exhibit 5.25 -- Static
Functionality Test of Valve-Stem-Mounted TPMS (RROD)

![](media/image48.wmf){width="6.566666666666666in"
height="3.9715277777777778in"}

For this system, Exhibit 5.25 shows that an initial leak rate of 1.5
psi/minute on the RROD resulted in the initial warning indicating at 84
psi and a second warning indicating at 72 psi, as shown by the Marker
channel. These readings generally correspond to the manufacturer's
specification of an initial warning indicator at 12.5 percent below CIP
(87.5 psi for our test) and a second indicator at 25 percent below CIP
(75 psi for our test).

Exhibit 5.26 shows the results of the dynamic functionality test for
this same system. The initial warning was indicated at 86 psi (marker
signal not shown) and a second warning indicator given at 74 psi (marker
shown), which correspond to the manufacturer's warning specifications of
87.5 psi and 75 psi respectively for our test CIP.

[]{#__RefHeading___Toc149980589 .anchor}Exhibit 5.26 -- Dynamic
Functionality Test of Valve-Stem-Mounted TPMS (RROD)

![](media/image49.wmf){width="6.566666666666666in"
height="4.010416666666667in"}

Exhibit 5.27 shows similar results for a static functionality test of a
wheel-mounted TPMS. With this system, the manufacture sets an initial
"slow air leak" warning to be indicated when the pressure in the tire
decreases by 3 psi. A second warning for "low pressure" is set to
indicate a warning when the tire pressure reaches a user-adjustable
level, in our case set at 20 psi below CIP (or 80 psi). The measurements
in Exhibit 5.27 generally correspond to the manufacturer's specification
with an initial warning indicator at 98 psi in our test and a second
indicator at 79 psi in our test.

[]{#__RefHeading___Toc149980590 .anchor}Exhibit 5.27 -- Static
Functionality Test of Wheel-Mounted TPMS (RROD)

![](media/image50.wmf){width="6.566666666666666in"
height="3.984027777777778in"}

Exhibit 5.28 shows the results of a dynamic functionality test for the
same wheel-mounted TPMS in Exhibit 5.27. In this test, an initial
warning is indicated for a "slow leak" at 98 psi (not indicated by the
marker) and a "low pressure" warning is indicated at 80 psi (as noted
above, the specification from the manufacturer called for the first
warning at 3 psi below target and a second warning at 20 psi below
target).

[]{#__RefHeading___Toc149980591 .anchor}Exhibit 5.28 -- Dynamic
Functionality Test of Wheel-Mounted TPMS (RROD)

![](media/image51.wmf){width="6.566666666666666in"
height="3.984027777777778in"}

In general, each system tested, valve- or wheel-mounted, had the
base-level functionality expected based on their individual designs. All
provided warnings, although the deviation from the expected warning
pressure varied from system to system and tire to tire given a slow leak
(approximately 1.5 psi/min initial rate). The exact deviations from the
expected warning thresholds were tested and analyzed in the warning
threshold level tests in the next section.

Static and dynamic functionality tests were not performed on the
tire-mounted TPMS because the systems tested did not use in-cab displays
to provide a real-time warning of under-inflation of the tires. As
described earlier in the report, they use a handheld or drive-through
gate reader to measure and record individual tire pressures.

### Threshold Warning Level Test

The objective of the threshold warning level tests was to understand the
threshold levels at which TPMS indicate a low tire pressure warning. For
the testing of each TPMS, the test procedure in Exhibit 5.29 was used.

[]{#__RefHeading___Toc149980592 .anchor}Exhibit 5.29 -- TPMS Threshold
Warning Level Test Procedures

  --------------------------------------------------------------------------
  **Step     **Procedure**
  Number**   
  ---------- ---------------------------------------------------------------
  1          Set all tires to Cold Inflation Pressure (CIP=100 psi), Create
             new test data file

  2          Set test manifold to proper positions

  3          Start Data Recorder, Sample at 10 Hz

  4          Record Starting Tire Temperatures

  5          Deflate RFS tire to 2 psi above expected warning threshold as
             indicated by the manufacturer.

  6          Drive vehicle at 45 mph for 20 minutes (2 laps) around the high
             speed track

  7          Stop Vehicle

  8          Reset test tire pressure to 2 psi above expected warning
             threshold

  9          Drive vehicle at 45 mph for 10 minutes (1 lap) around high
             speed track

  10         Press marker switch when system indicates low tire pressure

  11         Stop vehicle

  12         If no warning observed, decrease tire pressure 1 psi below
             previously set value

  13         Repeat 9-12 until warning is observed or tire pressure reaches
             40% below CIP for drive/trailer tires or 25% below CIP for
             steer tires (for those systems which have multiple warning
             levels, repeat until all warning level thresholds are met)

  14         Stop Data Recorder

  15         Record file name and stop number

  16         Wait 30 minutes, or until tires return to temperatures recorded
             in Step 4

  17         Repeat 1-16 for LFID, RROD, RFIT, and LROT
  --------------------------------------------------------------------------

Exhibit 5.30 shows the results of a threshold warning level test on an
Advantage PressurePro valve-stem-mounted TPMS installed on the
tractor-trailer vehicle platform.

Exhibit 5.30 -- Advantage PressurePro Valve-Stem-Mounted TPMS Threshold
Warning

[]{#refheading___toc149980593 .anchor}Level Test

![](media/image52.wmf){width="6.585416666666666in"
height="3.990972222222222in"}

As shown in Exhibit 5.30, the test tire was set at 90 psi (2 psi above
the expected warning threshold). The test vehicle was driven at 45 mph
for two laps (7.5 miles each) around the test track. The pressure was
then reset at 90 psi (down from a hot inflation pressure of 96 psi) and
the vehicle was driven for another lap at 45 mph. The system did not
indicate any warning during that lap; therefore, the pressure was
reduced an additional 1 psi, and an additional 45 mph lap was driven.
This process was repeated until a warning was indicated at 87 psi just
after beginning the fourth test lap, as indicated in Exhibit 5.30 by the
Marker channel. Additional tests were performed on the RFS, LFID, RFIT,
and LROT tires for this system, and on another valve-stem-mounted system
(IVTM) installed on the motorcoach platform. The results are shown in
Exhibit 5.31.

[]{#__RefHeading___Toc149980594 .anchor}Exhibit 5.31 --
Valve-Stem-Mounted TPMS Threshold Warning Level Tests Results

  ---------------------------- ------------------------------------------
  **Advantage PressurePro --   
  Tractor-Trailer**            

  **Tire Position**            **1^st^ Warning Threshold (psi)**

  RFS                          88

  LFID                         87

  RROD                         87

  RFIT                         88

  LROT                         87
  ---------------------------- ------------------------------------------

The results in Exhibit 5.31 show that for each system, the warning
thresholds were consistent across all of the tires tested. The Advantage
PressurePro TPMS installed in the tractor-trailer was set up to provide
an initial warning at 12.5 percent below CIP (or 87.5 psi), which is
consistent with the data collected.[^15] The TPMS installed in the
motorcoach provided an initial low-pressure warning between 86 and 88
psi and a second low-pressure warning between 74 and 77 psi.

Exhibit 5.32 provides a chart of a threshold warning level test for a
wheel-mounted TPMS installed on the tractor-trailer vehicle platform.

[]{#__RefHeading___Toc149980595 .anchor}Exhibit 5.32 -- Wheel-Mounted
TPMS Threshold Warning Level Test

![](media/image53.wmf){width="6.585416666666666in"
height="3.9972222222222222in"}

As shown in Exhibit 5.32, the wheel-mounted TPMS tested initiated a
warning at 82 psi. This occurred during the first 45-mph lap run after
the two initial warm-up laps. Additional tests were performed on the
RFS, LFID, RFIT, and LROT tires for this system, and on a different
wheel-mounted system installed on the motorcoach platform. The results
are shown in Exhibit 5.33.

The expected warning threshold for the TPMS installed in the
tractor-trailer platform was the default setting of 80 psi (20 psi below
CIP) for the tractor tires and 70 psi (30 psi below CIP) for the trailer
tires.[^16] The expected warning threshold for the TPMS installed in the
motorcoach platform was 90 psi (20 psi below CIP), also the default
setting.Error: Reference source not found

[]{#__RefHeading___Toc149980596 .anchor}Exhibit 5.33 --
Valve-Stem-Mounted TPMS Threshold Warning Level Tests Results

  ------------------------- ---------------------------------------------
  **Tire-SafeGuard--        
  Tractor-Trailer**         

  **Tire Position**         **1^st^ Warning Threshold (psi)**

  RFS                       84

  LFID                      81

  RROD                      82

  RFIT                      71

  LROT                      71
  ------------------------- ---------------------------------------------

Each of the four TPMS tested provided warnings with a very good
correlation with the expected values and between the tire assemblies
tested.

### Loaded Test at High Speed

This test examined the effects of tire heating, due to sustained
high-speed driving, on the warning indicator of the TPMS. As vehicles
are driven, heat builds up in the tire due to a number of
factors---mostly as a result of rolling friction with the road surface,
but also due to flexing the sidewall of the tire (which is increased if
the tire is under inflated), heat from braking and other radiant
sources, and tire scrubbing during turning and cornering. This increase
in heat results in an increase of pressure inside the tire. Exhibit 5.34
shows an example of this effect.

[]{#__RefHeading___Toc149980597 .anchor}Exhibit 5.34 -- Example of
Pressure Increase Due to Sustained High-speed Driving

![](media/image54.wmf){width="6.585416666666666in"
height="3.9972222222222222in"}

To accommodate this effect, some TPMS measure the tire temperature and
compensate for the increased pressure by calculating an equivalent CIP.
This test is designed to determine, for the TPMS technologies selected
for testing here, whether they compensate for the increased pressure as
a result of sustained high-speed driving. Exhibit 5.35 shows the general
test procedures performed.

[]{#__RefHeading___Toc149980598 .anchor}Exhibit 5.35 -- TPMS Loaded Test
at High-Speed Test Procedures

  --------------------------------------------------------------------------
  **Step     **Procedure**
  Number**   
  ---------- ---------------------------------------------------------------
  1          Set all tires to Cold Inflation Pressure (CIP=100 psi), Create
             new test file

  2          Set manifold to proper positions

  3          Start Data Recorder, Sample at 10 Hz

  4          Record Starting Tire Temperatures

  5          Deflate RFS tire to 2 psi below the average warning threshold
             determined in Test #1

  6          Drive the vehicle at 45 mph for 10 minutes (1 lap) around HST

  7          Press marker switch when system indicates low tire pressure

  8          If no warning observed, stop vehicle, reduce tire pressure an
             additional 2 psi, repeat Steps 6-7 until a warning is observed
             or tire reaches 40% below CIP for drive/trailer tires or 25%
             below CIP for steer tires

  9          Drive vehicle at 75 mph for 22.5 miles (3 laps) around HST

  10         Press marker switch again if/when low tire pressure indicator
             is extinguished

  11         Stop Data Recorder

  12         Record file name and stop number

  13         If the low tire pressure warning is maintained, restore tire to
             100 psi

  14         Drive vehicle at 45 mph around HST until warning indicator is
             extinguished

  15         Wait 30 minutes, or until tires return to temperatures recorded
             in Step 4

  16         Repeat 1-15 for LFID, RROD, RFIT, and LROT
  --------------------------------------------------------------------------

Exhibit 5.36 illustrates the pressure changes over time for a
valve-stem-mounted TPMS on the tractor-trailer vehicle platform.

[]{#__RefHeading___Toc149980599 .anchor}Exhibit 5.36 --
Valve-Stem-Mounted TPMS Loaded Test at High Speed

![](media/image55.wmf){width="6.570833333333334in"
height="4.477777777777778in"}

In Exhibit 5.36, the pressure in the RROD tire was deflated to 86 psi,
triggering a warning indicator by the valve-stem-mounted TPMS. The fully
loaded vehicle then was driven at 75 mph around the high-speed test
track for three laps. Exhibit 5.36 shows that the temperature for both
the RROD and the RRID increase during this sustained high-speed driving.
As shown in Exhibit 5.36, the warning indicator was extinguished when
the temperature increased sufficiently to cause an increase in tire
pressure to 89 psi.

Additional tests were performed on the RFS, LFID, RFIT, and LROT tires
for this system, and on a valve-stem-mounted system installed on the
motorcoach platform. The results are shown in Exhibit 5.37.

[]{#__RefHeading___Toc149980600 .anchor}Exhibit 5.37 --
Valve-Stem-Mounted TPMS Loaded Test at High Speeds Results

+-------------+-------------+-------------+-------------+-------------+
| **Tire      | **Initial   | **          | **Warning   | **Final     |
| Position**  | Warning     | Temperature | Status      | Pressure    |
|             | Pressure    | Change      | After       | (psi)**     |
|             | (psi)**     | (degrees    | Driving**   |             |
|             |             | F)**        |             |             |
|             |             |             | *           |             |
|             |             |             | *(ON/OFF)** |             |
+-------------+-------------+-------------+-------------+-------------+
| Advantage   |             |             |             |             |
| PressurePro |             |             |             |             |
| --          |             |             |             |             |
| Trac        |             |             |             |             |
| tor-Trailer |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+
| RFS         | 86          | +21         | OFF         | 89          |
+-------------+-------------+-------------+-------------+-------------+
| LFID        | 86          | +16         | OFF         | 88          |
+-------------+-------------+-------------+-------------+-------------+
| RROD        | 86          | +15         | OFF         | 89          |
+-------------+-------------+-------------+-------------+-------------+
| RFIT        | 86          | +20         | OFF         | 89          |
+-------------+-------------+-------------+-------------+-------------+
| LROT        | 86          | +14         | ON          | 89          |
+-------------+-------------+-------------+-------------+-------------+
| IVTM --     |             |             |             |             |
| Motorcoach  |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+
| RFS         | 76          | +33         | ON          | 82          |
+-------------+-------------+-------------+-------------+-------------+
| LFID        | 75          | +13         | ON          | 72\*        |
+-------------+-------------+-------------+-------------+-------------+
| RTAG        | 76          | +30         | ON          | 80          |
+-------------+-------------+-------------+-------------+-------------+
| \* Note:    |             |             |             |             |
| Although    |             |             |             |             |
| this test   |             |             |             |             |
| was         |             |             |             |             |
| conducted   |             |             |             |             |
| on the same |             |             |             |             |
| day as the  |             |             |             |             |
| RFS and     |             |             |             |             |
| RTAG, the   |             |             |             |             |
| ambient     |             |             |             |             |
| temperature |             |             |             |             |
| for the     |             |             |             |             |
| LFID test   |             |             |             |             |
| fell to 11  |             |             |             |             |
| degrees F   |             |             |             |             |
| -- due to   |             |             |             |             |
| the sunset, |             |             |             |             |
| possibly    |             |             |             |             |
| resulting   |             |             |             |             |
| in          |             |             |             |             |
| erroneous   |             |             |             |             |
| readings by |             |             |             |             |
| the data    |             |             |             |             |
| collection  |             |             |             |             |
| equipment.  |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+

As shown in Exhibit 5.37, the valve-stem-mounted TPMS installed on the
tractor-trailer platform did not compensate for increased tire pressure
due to heating, which resulted in warnings being extinguished once the
pressure exceeds the warning threshold. However, the valve-stem-mounted
TPMS installed on the motorcoach platform shows that the warning
indicators remained on during the test. The manufacturer indicated the
use of two methods to compensate for this effect. First, the
manufacturer uses a hysteresis effect where a warning is only
extinguished once the pressure exceeds the warning threshold by a
specific amount. According to the manufacturer:

> "For example, if the pressure falls down below the under inflation
> threshold of -20% and then the tire is filled up again, the pressure
> must be above -15 %. 100 psi ref. pressure -\> pressure drop to 80 psi
> -\> filling up to 85 psi -\> warning disappears. The wheel module
> transmits an actual pressure value when the new measured value is at
> least a 4 psi change than the last transmitted value. Then the wheel
> module will constantly update the ECU until the pressure is
> stabilized."[^17]

To translate, in a vehicle with a target pressure of 100 psi deflating
the tire to 80 psi triggers a warning indicator. This warning indicator
would not be extinguished until the pressure increased above 85 psi.
Secondly, the manufacturer compensates for temperature by a proprietary
algorithm:

> "We have on the ECU an algorithm designed to determine when a vehicle
> is starting out cold, then when pressure increases which causes the
> tire to run hot. This prevents false alarms and accurate reporting of
> over and under inflation and address the issue of temperature pressure
> relationships."Error: Reference source not found

Exhibit 5.38 shows a loaded test at high speed for a wheel-mounted TPMS
on the tractor-trailer vehicle platform.

[]{#__RefHeading___Toc149980601 .anchor}Exhibit 5.38 -- Wheel-Mounted
TPMS Loaded Test at High Speed

![](media/image56.wmf){width="6.570833333333334in"
height="3.9972222222222222in"}

As shown in Exhibit 5.38, the wheel-mounted TPMS also exhibited
increased pressure effects due to tire heating, but the warning
indication was discontinued once the pressure reached the warning
threshold.

Additional tests were performed on the RFS, LFID, RFIT, and LROT tires
for this system, and on a wheel-mounted SmarTire system installed on the
motorcoach platform. The results are shown in Exhibit 5.39.

[]{#__RefHeading___Toc149980602 .anchor}Exhibit 5.39 -- Wheel-Mounted
TPMS Loaded Test at High Speeds Results

+-------------+-------------+-------------+-------------+-------------+
| **Tire      | **Initial   | **          | **Warning   | **Final     |
| Position**  | Warning     | Temperature | Status      | Pressure    |
|             | Pressure    | Change      | After       | (psi)**     |
|             | (psi)**     | (degrees    | Driving**   |             |
|             |             | F)**        |             |             |
|             |             |             | *           |             |
|             |             |             | *(ON/OFF)** |             |
+=============+=============+=============+=============+=============+
| Tir         |             |             |             |             |
| e-SafeGuard |             |             |             |             |
| --          |             |             |             |             |
| Trac        |             |             |             |             |
| tor-Trailer |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+
| RFS         | 78          | +20         | ON          | 82          |
+-------------+-------------+-------------+-------------+-------------+
| LFID        | 78          | +12         | OFF         | 81          |
+-------------+-------------+-------------+-------------+-------------+
| RROD        | 78          | +3          | OFF         | 79          |
+-------------+-------------+-------------+-------------+-------------+
| RFIT        | 68          | +16         | OFF         | 70          |
+-------------+-------------+-------------+-------------+-------------+
| LROT        | 68          | +22         | ON          | 72          |
+-------------+-------------+-------------+-------------+-------------+
| SmarTire -- |             |             |             |             |
| Motorcoach  |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+
| RFS         | 88          | +16         | OFF         | 93          |
+-------------+-------------+-------------+-------------+-------------+
| LFID        | 88          | +26         | ON          | 92          |
+-------------+-------------+-------------+-------------+-------------+
| RTAG        | 88          | +24         | OFF         | 94          |
+-------------+-------------+-------------+-------------+-------------+

In Exhibit 5.39, the wheel-mounted system on the tractor-trailer
platform showed a significant amount of variation in the results. The
warning indicator remained on during the tests on the RFS and
LROT---there was a significant increase in temperature and an increase
in pressure above the warning thresholds of 80 psi on the tractor tires
and 70 psi on the trailer tires. In contrast, the warning indicator was
extinguished on tests of the LFID, RROD, and RFIT, which had lower
temperature increases and resulting lower pressure increases. This might
be a result of the ability of the compensation algorithm employed to
detect and compensate for large and rapid increases in temperature but
not for the more gradual increases.

The TPMS installed in the motorcoach platform also exhibited some
variation in the test results, with the RFS and RTAG warning indicators
being extinguished in their respective tests, but the LFID warning
indicator not being extinguished in its test. However, as Exhibit 5.16
shows, the pressure in the LFID only reached 92 psi (as opposed to 93
psi and 94 psi for the RFS and RTAG) before the test time expired.
Therefore it is unknown whether the warning indicator would be
extinguished during further driving.

Exhibit 5.40 shows the loaded test at high speed of an eTire TPMS
installed on the tractor-trailer platform. As we noted, the eTire TPMS
selected for this test program did not have an in-cab display available,
but relied instead on a handheld or gate reader to capture pressure
readings. There was no practical way to observe while the CMV was being
driven on the track when warnings were or were not indicated, so the
test procedures for this system were modified slightly to enable manual
reading of the test tire. The test tire's sensor patch was read with the
manual reader before the test, after the warm-up lap, and again after
completing three 75 mph laps around the test track. Exhibit 5.40 shows
the data collected from this test on the RROD tire.

[]{#__RefHeading___Toc149980603 .anchor}Exhibit 5.40 - eTire TPMS Loaded
Test at High Speed

![](media/image57.wmf){width="6.585416666666666in"
height="3.977777777777778in"}

In Exhibit 5.40, the handheld reader recorded the temperature read by
the sensor, the pressure read by the sensor, and the corrected pressure
as a result of the sensor compensating for the temperature inside the
tire. Exhibit 5.40 shows that the eTire TPMS sensor compensated for the
increased temperature and pressure due to sustained high-speed driving.
Exhibit 5.41 show the results of each of the tests for the tire-mounted
TPMS.

[]{#__RefHeading___Toc149980604 .anchor}Exhibit 5.41 -- eTire TPMS
Loaded Test at High Speeds Results

<table>
<colgroup>
<col style="width: 9%" />
<col style="width: 9%" />
<col style="width: 9%" />
<col style="width: 12%" />
<col style="width: 9%" />
<col style="width: 9%" />
<col style="width: 10%" />
<col style="width: 8%" />
<col style="width: 9%" />
<col style="width: 11%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="10"><strong>eTire – Tractor-Trailer</strong></td>
</tr>
<tr class="even">
<td></td>
<td colspan="3"><strong>Start</strong></td>
<td colspan="3"><strong>After Warm Up</strong></td>
<td colspan="3"><strong>After High-Speed Driving</strong></td>
</tr>
<tr class="odd">
<td><strong>Tire Position</strong></td>
<td><strong>Read Temp. (deg. F)</strong></td>
<td><p><strong>Read Press.</strong></p>
<p><strong>(psi)</strong></p></td>
<td><strong>Corrected Press. (psi)</strong></td>
<td><strong>Read Temp. (deg. F)</strong></td>
<td><p><strong>Read Press.</strong></p>
<p><strong>(psi)</strong></p></td>
<td><strong>Corrected Pressure (psi)</strong></td>
<td><strong>Read Temp. (deg. F)</strong></td>
<td><p><strong>Read Press.</strong></p>
<p><strong>(psi)</strong></p></td>
<td><strong>Corrected Press. (psi)</strong></td>
</tr>
<tr class="even">
<td>RFS</td>
<td colspan="3">Not Recorded</td>
<td>95</td>
<td>98</td>
<td>80</td>
<td>131</td>
<td>107</td>
<td><strong>81</strong></td>
</tr>
<tr class="odd">
<td>LFID</td>
<td>87</td>
<td>96</td>
<td>78</td>
<td>89</td>
<td>96</td>
<td>79</td>
<td>107</td>
<td>98</td>
<td><strong>76</strong></td>
</tr>
<tr class="even">
<td>RROD</td>
<td>111</td>
<td>94</td>
<td>73</td>
<td>107</td>
<td>92</td>
<td>72</td>
<td>122</td>
<td>97</td>
<td><strong>74</strong></td>
</tr>
<tr class="odd">
<td>RFIT</td>
<td>93</td>
<td>91</td>
<td>73</td>
<td>98</td>
<td>95</td>
<td>75</td>
<td>105</td>
<td>97</td>
<td><strong>75</strong></td>
</tr>
<tr class="even">
<td>LROT</td>
<td>95</td>
<td>91</td>
<td>71</td>
<td>96</td>
<td>92</td>
<td>72</td>
<td>107</td>
<td>94</td>
<td><strong>73</strong></td>
</tr>
</tbody>
</table>

Exhibit 5.41 shows that the eTire TPMS appears to compensate effectively
for the increased tire temperatures and pressures as a result of tire
heating due to sustained high-speed driving.

### Disablement Test

This test determines the system's ability to provide a warning indicator
if/when it is disabled either by an intentional act or as a result of a
failure of a system or component. Based on experience with each system,
the specific configuration of the system, and the possible ways the
system might be disabled intentionally or non-intentionally, several
disablement modes were tested for each system.

Exhibit 5.42 shows the disablement modes tested for the
valve-stem-mounted TPMS installed on the tractor-trailer vehicle
platform.

[]{#__RefHeading___Toc149980605 .anchor}Exhibit 5.42 -- Advantage
PressurePro Disablement Results

+------+-------------------+----------------------+-------------------+
| **A  |                   |                      |                   |
| dvan |                   |                      |                   |
| tage |                   |                      |                   |
| Pre  |                   |                      |                   |
| ssur |                   |                      |                   |
| ePro |                   |                      |                   |
| --   |                   |                      |                   |
| T    |                   |                      |                   |
| ract |                   |                      |                   |
| or-T |                   |                      |                   |
| rail |                   |                      |                   |
| er** |                   |                      |                   |
+------+-------------------+----------------------+-------------------+
| **   | **Purpose**       | **Description**      | **Result**        |
| Mode |                   |                      |                   |
| \#** |                   |                      |                   |
+------+-------------------+----------------------+-------------------+
| 1    | Simulate Loose    | Slightly unscrew     | No response from  |
|      | Sensor            | sensor from RROD     | system            |
|      |                   | valve stem (ensure   |                   |
|      |                   | air leakage can be   |                   |
|      |                   | heard)               |                   |
+------+-------------------+----------------------+-------------------+
| 2    | Simulate          | Completely unscrew   | Display indicated |
|      | Disconnected      | sensor from LROT     | warning of 0 psi  |
|      | Sensor            | valve stem           | immediately       |
+------+-------------------+----------------------+-------------------+
| 3    | Simulate          | Completely unscrew   | System lost       |
|      | Disconnected      | antenna from outside | signal from RROT  |
|      | Trailer Antenna   | rear of tractor cab  | and RRIT sensors  |
+------+-------------------+----------------------+-------------------+
| 4    | Simulate          | Completely unscrew   | System lost       |
|      | Disconnected      | antenna from display | signal with all   |
|      | Display Antenna   | unit in cab          | tires except RFS, |
|      |                   |                      | RFS, and RROD     |
+------+-------------------+----------------------+-------------------+
| 5    | Simulate Swapped  | Swap RROD and LFID   | System swapped    |
|      | Sensors           | sensors              | pressure readings |
+------+-------------------+----------------------+-------------------+
| 6    | Simulate Lost     | Quickly remove RROD  | Display indicated |
|      | Sensor            | sensor and throw it  | warning of        |
|      |                   | \> 100 ft            |                   |
|      |                   |                      | "\-\--"           |
|      |                   |                      | immediately       |
+------+-------------------+----------------------+-------------------+
| 7    | Simulate Impact   | Strike LFID sensor   | No response from  |
|      | from Hammer       | with hammer once     | system            |
+------+-------------------+----------------------+-------------------+

Exhibit 5.42 shows the requirement for utilizing remote antenna
assemblies on the rear of the tractor and attached to the
display---because disconnecting these antennas resulted in loss of
signal from several sensors. The test also showed that the system is
able to detect a lost or disconnected sensor and displays this as a
reading of 0 psi.

Exhibit 5.43 shows the disablement modes tested for the
valve-stem-mounted TPMS installed on the motorcoach platform.

[]{#__RefHeading___Toc149980606 .anchor}Exhibit 5.43 -- IVTM Disablement
Results

  --------------------------------------------------------------------------------
  **IVTM --                                                    
  Motorcoach**                                                 
  -------------- -------------------- ------------------------ -------------------
  **Mode \#**    **Purpose**          **Description**          **Result**

  1              Simulate Swapped     Switch RROD and LROD     System switched
                 Sensors              sensors                  pressure readings
                                                               for tires

  2              Simulate Loose       Slightly unscrew sensor  Display indicated
                 Sensor               from RFS valve stem      low pressure with
                                      (ensure air leakage can  "STOP" light
                                      be heard)                illuminated

  3              Simulate             Completely unscrew       Tire leaked slowly
                 Disconnected Sensor  sensor from RFS valve    and display
                                      stem                     indicated low
                                                               pressure with
                                                               "STOP" light
                                                               illuminated

  4              Simulate Severed     Cut hose connecting the  Tire leaked and
                 Hose                 RFS sensor to the RFS    display indicated
                                      valve stem               low pressure with
                                                               "STOP" light
                                                               illuminated

  5              Simulate Impact from Strike RFS sensor with   No affect on system
                 Hammer               hammer once              
  --------------------------------------------------------------------------------

In Exhibit 5.43, the system displayed a "STOP" indicator when it
detected a disconnected or loose sensor, or when it detected a
disconnected input hose. This result was expected.

Both valve-stem-mounted systems in Exhibits 5.42 and 5.43 display sensor
readings when the sensors have been switched between tires but pressures
indicated correspond to the incorrect tire position. Although expected,
this highlights an issue with valve-stem-mounted systems as they are
often removed to replace tires, inspect brakes, or perform other vehicle
maintenance. Therefore, either careful records must be kept as to which
sensor goes on which tire, or the systems must be "retrained" after the
maintenance is performed. While sounding straightforward, in a
maintenance garage with many tire technicians mechanics or in a shop
where some of the technicians are not familiar with the TPMS, this could
prove difficult.

Exhibit 5.44 shows the disablement modes tested for a wheel-mounted TPMS
installed on the tractor-trailer vehicle platform.

[]{#__RefHeading___Toc149980607 .anchor}Exhibit 5.44 -- Tire-SafeGuard
Disablement Results

  ------------------- -------------------- ----------------------- -------------------
  **Tire-SafeGuard --                                              
  Tractor-Trailer**                                                

  **Mode \#**         **Purpose**          **Description**         **Result**

  1                   Simulate Fractured   Install sensor which    System indicated
                      Sensor Due to Damage was accidentally        104 psi with 100
                      by Tire Mounting     damaged by the tire     psi in tire
                      Machine              mounting machine during 
                                           installation.           

  2                   Simulate             Completely unscrew      No readings from
                      Disconnected Tractor tractor antenna cable   sensors
                      Antenna              from tractor receiver   

  3                   Simulate             Completely unscrew RX   No readings from
                      Disconnected Trailer antenna cable from      sensors
                      RX Antenna           trailer receiver        

  4                   Simulate             Completely unscrew TX   No readings from
                      Disconnected Trailer antenna cable from      sensors
                      TX Antenna           trailer receiver        

  5                   Simulate Swapped     Switch LFOT wheel/tire  System indicated
                      Trailer Sensors      with RRIT wheel/tire    pressure of new
                                           (do not re-train)       tire position in
                                                                   original tire
                                                                   position

  6                   Simulate Swapped     Switch LFOT wheel/tire  System indicated
                      Sensors Between      with LROD wheel/tire    pressure of new
                      Tractor and Trailer  (do not re-train)       tire position in
                                                                   original tire
                                                                   position

  7                   Simulate Loss of     Disconnect battery,     System functioned
                      Battery Power        wait 10 minutes,        normally
                                           reconnect battery.      
  ------------------- -------------------- ----------------------- -------------------

Exhibit 5.45 shows the disablement modes tested for the wheel-mounted
SmarTire TPMS installed on the motorcoach platform.

[]{#__RefHeading___Toc149980608 .anchor}Exhibit 5.45 -- SmarTire
Disablement Results

  -------------------------------------------------------------------------------
  **SmarTire --                                               
  Motorcoach**                                                
  -------------- -------------------- ----------------------- -------------------
  **Mode \#**    **Purpose**          **Description**         **Result**

  1              Simulate Fractured   Install sensor which    No response from
                 Sensor Due to Damage was accidentally        system, system
                 by Tire Mounting     damaged by the tire     continued to read
                 Machine              mounting machine during normally.
                                      installation.           

  2              Simulate             Completely unscrew one  System functioned
                 Disconnected One     antenna cable from      normally
                 Antenna While        receiver                
                 Stationary                                   

  3              Simulate             Completely unscrew both "E1" Message
                 Disconnected Both    antennas from receiver  Displayed
                 Antennas             and drive at 45 mph     

  4              Simulate             Completely unscrew      Display indicated
                 Disconnected One     antenna #1 from         warning of low
                 Antenna While In     receiver and drive at   pressure in RFS.
                 Motion               45 mph and initiate a   
                                      leak in RFS and RTAG    

  5              Simulate             Completely unscrew      Display indicated
                 Disconnected One     antenna #2 from         warning of low
                 Antenna While In     receiver and drive at   pressure in RTAG.
                 Motion               45 mph and initiate a   
                                      leak in RFS and RTAG    
  -------------------------------------------------------------------------------

In Exhibit 5.45, the system responded with an error message when it
could not receive signals from any sensors due to disconnection of the
antennas. When only the front antenna was disconnected, the RFS sensor
did not record a low-pressure warning, but the RTAG sensor did (Mode
#5). Conversely, when the rear antenna was disconnected, the RTAG sensor
did not record a low-pressure warning, but the RFS sensor did (Mode #4).

### Operator Interface Evaluation

Advantage PressurePro used an aftermarket-type display interface that
attached by suction to the windshield of the cab, as shown in Exhibit
5.46. The display had a graphic of a tractor and trailer with an LED
display for the pressure and warning lights for each of the tires. If
more than one tire sensor provides a warning, the system cycles through
each affected tire. A flashing warning light and an audible alarm alerts
the driver to low pressure. The light flashes on the LED display once
per second for the first alert level (12.5 percent below set CIP) and
twice per second for the second alert level (25 percent below set CIP).
The system also provides alerts for low sensor batteries, missing
sensors, and reminder alerts beyond the initial warning for low
pressure. In addition, the display unit includes a number of buttons to
control various functions of the system. Of interest, the up/down arrow
keys allow the operator to check individual tire pressures, and the F/B
button allows the operator to monitor only the front or back vehicle in
the case of combination units or on an RV towing a vehicle.

[]{#__RefHeading___Toc149980609 .anchor}Exhibit 5.46 -- Advantage
PressurePro Operator Interface

![ Exhibit 5.46 is a picture of the Advantage Pressurepro display
mounted to the windshield of a vehicle. The display has a graphic of a
tractor and trailer with an LED numeric display for the pressure and LED
warning lights for each of the tires. In addition, the display unit
includes a number of buttons to control various functions of the system
including up/down arrow keys, on and set keys and an F/B button.
](media/image58.jpeg){width="4.463779527559055in"
height="2.591732283464567in"}![ Exhibit 5.46 is a picture of the
Advantage Pressurepro display mounted to the windshield of a vehicle.
The display has a graphic of a tractor and trailer with an LED numeric
display for the pressure and LED warning lights for each of the tires.
In addition, the display unit includes a number of buttons to control
various functions of the system including up/down arrow keys, on and set
keys and an F/B button.
](media/image59.png){width="1.6311023622047245in"
height="0.7019685039370078in"}

The IVTM used an LCD display in conjunction with a large "STOP" light, a
"SLOW" light with a turtle icon, and an audible alarm. Moderate
inflation problems result in a "SLOW" or turtle light illumination and
an audible signal that sounds for a period of 10 minutes. Pressing the
"?" button multiple times displays in sequence the position of the
affected tire, tire pressure, and an action graphic on the LCD of either
a wrench (system maintenance required) or tire pump (inflation
required). An additional LCD graphic indicates a creeping pressure loss.
A major inflation issue results in a "STOP" light illumination and a
one-minute audible signal similar to the 10-minute audible signal,
except for duration. In the event of multiple warnings, the system
cycles through each affected tire. The operator can inspect the status
of any sensor-equipped tire by pressing an inspection button (magnifying
glass and tire icon). Exhibit 5.47 shows this display.

![Exhibit 5.47 is a picture of the IVTM display which has an LED display
in conjunction with a large "STOP" light, a "SLOW" light with a turtle
icon, a "?", a tire pump graphic and an iinspection button (magnifying
glass and tire icon).](media/image60.jpeg){width="3.954724409448819in"
height="3.0673228346456693in"}

[]{#__RefHeading___Toc149980610 .anchor}Exhibit 5.47 -- IVTM Operator
Interface

The test drivers commented that the interface in Exhibit 5.47 for the
IVTM was difficult to read in the daytime. The black and red display, in
addition to the "STOP" and "SLOW" lights, was not bright enough to
overcome the high-light conditions during the daytime. However, this
display worked exceptionally well during the nighttime testing.

The operator interface for Tire-SafeGuard, shown in Exhibit 5.48,
includes an LCD display designed to be mounted onto the dashboard. It
uses a single LCD screen for both the tractor and trailer displays
(cycling through the tires on each in turn) in conjunction with an
audible alarm. In the event of an inflation problem, the system sounds
an alarm for 8 seconds and displays the location of the tire, an icon
indicating the warning type (low pressure, slow air leak, high tire
pressure, or high temperature), the measured tire pressure, and the tire
temperature. In the event of multiple warnings, the system cycles
through each affected tire continuously until the condition is remedied.
Warnings could be temporarily cleared using a small button on the front
panel, but the underlying condition persisted. The warnings reappeared
during the next tire pressure data transmission cycle.

[]{#__RefHeading___Toc149980611 .anchor}![ Exhibit 5.48 is a picture of
the Tire SafeGuard display that includes an LCD display that indicates
the location of the tire, an icon indicating the warning type (low
pressure, slow air leak, high tire pressure, or high temperature), the
measured tire pressure, and the tire temperature. There is also a small
button and a yellow LED light on the front
panel.](media/image16.jpeg){width="3.5681102362204724in"
height="1.7389763779527558in"}Exhibit 5.48 -- Tire-SafeGuard Operator
Interface

Exhibit 5.49 shows the operator interface for SmarTire. It includes an
LCD with the image of a motorcoach and an audible alarm. A low pressure
or a deviation in pressure results in the illumination of the alert
indicator, sounding of an audible alarm, and (in the case of low
pressure) illumination of a low-pressure warning light (image of a flat
tire). The driver can acknowledge and turn off the audible alarm, but
the alert remains active until tires are properly re-inflated. A driver
can inspect the tire pressures, temperature, and pressure deviation
readings at any time.

[]{#__RefHeading___Toc149980612 .anchor}Exhibit 5.49 -- SmarTire
Operator Interface

![Exhibit 5.49 is a picture of the operator interface for SmarTire. It
includes an LCD with the image of a motorcoach and tire locations, a
numeric LCD display that indicates pressure a cycle button, alert
indicator and a small black
button.](media/image61.jpeg){width="3.1929133858267718in"
height="1.9200787401574804in"}![Exhibit 5.49 is a picture of the
operator interface for SmarTire. It includes an LCD with the image of a
motorcoach and tire locations, a numeric LCD display that indicates
pressure a cycle button, alert indicator and a small black
button.](media/image62.jpeg){width="3.25in"
height="1.9318897637795276in"}

The eTire was a tire-mounted TPMS, which did not use an in-cab display.
Instead, maintenance personnel would use a handheld reader to upload the
data, or the vehicle could be driven through a gate reader that uploaded
the tire pressure to an on-line tire management database (the gate
reader is evaluated in the next section). However, the handheld reader
assembly was used for the track testing. The handheld reader, shown in
Exhibit 5.50, was designed with a flat antenna on the end of a 1 ½-foot
pole and an LCD display and keypad on the other. Because the range of
the sensors' transmission was only a few inches, this design was
necessary to place the antenna between the tires of a dual assembly to
be able to read the tag of the inner dual.

To inspect tires by hand, maintenance personnel would navigate to the
proper "inspection" menu on the reader and "swipe" a tire's tag by
placing the flat antenna end 2 to 3 inches from the tire at the specific
location of the tag along the sidewall (as indicated by an affixed
decal). They would read the pressure and temperature of the tire from
the reader's LCD display. The reader could then be replaced in the
docking station, which (if connected to the Internet) would upload the
reading from the unit to the maintenance management database operated by
the system manufacturer for the fleet.

[]{#__RefHeading___Toc149980613 .anchor}![ Exhibit 5.50 is a picture of
the Etire handheld reader that has a flat antenna on one end of a 1
½-foot pole and an LCD display and keypad on the other. It is sitting in
a recharching/docking
cradle.](media/image21.jpeg){width="2.1251968503937007in"
height="4.636220472440945in"}Exhibit 5.50 -- eTire Handheld Reader
Interface

The technicians and test engineers found the handheld reader cumbersome
in operation and required a significant learning curve to use. The
software was text-based and the data entry from the handheld unit
required that its cradle be connected to a computer with Internet
access. However, per our discussions with the fleet that operated the
gate reader assembly used in our tests (see Section 5.2.6), the
maintenance personnel were pleased with the handheld reader's
performance.

### Gate Reader Evaluation

This test evaluates the performance and reliability of the drive-through
gate readers used with tire-mounted monitoring systems. The objective
was to determine the speed and consistency of the gate readers in
capturing pressures.

Only one system tested used an external gate reader, the eTire TPMS. Due
to the cost of installing a gate reader at the TRC test facility in
Columbus, the team used an existing gate reader facility operated by a
fleet in Indianapolis, IN, to perform this test. The fleet operator
graciously allowed the team to use this reader for 2 days in April 2005.

Exhibit 5.51 shows a photograph of the gate reader setup at the fleet in
Indianapolis.

[]{#__RefHeading___Toc149980614 .anchor}Exhibit 5.51 -- Photo of Gate
Reader Installation in Indianapolis, IN

![](media/image63.jpeg){width="6.50625in" height="4.772916666666666in"}

In Exhibit 5.51, the gate reader sensors are protected by concrete posts
to prevent accidental damage by vehicles. The eTire TPMS tested used a
passive tire tag (i.e., the tag was not powered, but received its power
from the measuring sensor), which resulted in a very short transmission
range. This required the sensors and concrete posts to be very close to
the wheel assemblies. This tight clearance limited the speeds that the
test tractor, with externally mounted rotary union test equipment, could
run through the gate reader to about 3 to 4 mph. Therefore, an
additional test to determine the vehicle speeds at which this system
could accurately record tire pressures was not performed.

The particular system tested used an on-line Web-based tool and backend
tire tag tracking system run by the TPMS manufacturer to log the
pressure readings from the gate reader or handheld reader. The gate
reader connected to a remote terminal located in the motor carrier's
maintenance office, where the tire pressure readings could be displayed
to personnel immediately. The data was then also forwarded via the
Internet to the backend tracking system run by the system manufacturer.
These tools enabled maintenance and management personnel to search a
Web-based system to find the status of vehicles and tires, add and
remove tires from the system, and manage the fleet's inventory of tires.

Exhibit 5.52 shows the results of the test runs conducted on the gate
reader.

[]{#__RefHeading___Toc149980615 .anchor}Exhibit 5.52 -- Gate Reader
Evaluation Results

  -------------- -------------- -------------- -------------- --------------
  **Vehicle**    **Passes       **Potential    **Actual Tires **Percentage
                 Through        Tires Read**   Read**         Read**
                 Gates**                                      

  **Tractor**    13             130            127            98%

  **Trailer**    13             104            103            99%
  -------------- -------------- -------------- -------------- --------------

Exhibit 5.52 shows that of the 26 passes through the gate reader, all
but 4 of the potential 234 tires were recorded. The limited speed at
which the test vehicle could traverse through the gate reader has
significant effects on the ability of the system to record signals from
the tire tags. Therefore, it is highly likely that these results were
skewed due to the test setup. However, in the project team's discussions
with the maintenance fleet, they did not express any issues related to
poor tire read rates, but stated they were satisfied with the system's
performance and effectiveness.

## Central Inflation Systems 

Central tire inflation systems use air from the reservoirs on the
vehicle that are filled by the engine-powered compressor. These systems
provide an on-board capability to monitor and inflate tires to proper
pressures. They also provide some ability to continue to operate with
small levels of leakage until repairs can be made. The systems use check
valves that isolate tires with severe pressure loss or catastrophic
failures to prevent the total loss of pressure from the primary and
secondary reservoirs. This protects the braking system from a total loss
of pressure, but will still allow the transfer of air between the
reservoir and the tires with moderate pressure differentials. The
systems also protect tires on a common fill circuit (i.e., an entire
axle) from individual tire failures and allows the tires on each circuit
to be monitored with visual indicator gauges.

The manufacturer of the Vigia CIS tested in this study advises that the
CIS will inflate tires if the preset tire pressure in any tire drops 3
psi from its calibrated level. If the tire continues to lose air, it
will maintain the calibrated pressure until the vehicle stops and the
engine is shut off. In the case of catastrophic air loss, the CIS are
equipped with check valves that prevent the vehicle's air supply from
falling below 70 psi. The installation requirements of the Vigia CIS
required an alteration of the instrumentation because it uses a rotary
union on the outboard side of each axle. The study's instrumentation
system, as described in previous sections, also used a rotary union to
transfer pressure and temperature data. Because it is not possible to
use two separate rotary unions simultaneously, the pressure transducers
on the DAS were connected with tees into the air lines of the Vigia CIS.
Tire temperatures could not be recorded without the use of the DAS'
instrumentation rotary unions, and therefore do not appear in the data
for the Vigia CIS.

Central tire inflation systems can be installed on motorcoaches,
straight trucks, and tractor-trailers. The PSI CIS was designed for
truck trailers only, while the Vigia CIS was designed for
tractor-trailers or motorcoaches. The PSI CIS was installed and tested
on the trailer of the tractor-trailer vehicle. The Vigia CIS was
installed and tested on the motorcoach.

### Functionality Tests

The static and dynamic functionality tests for central tire inflation
systems evaluate their ability to inflate a low tire as well as to
isolate an intact tire from a tire that has experienced a significant or
total loss of pressure. The systems were tested both statically to
determine basic functionality and dynamically to determine the effect of
the vehicle operation on the equalizer system's performance. Exhibit
5.53 summarizes central tire inflation system functionality test
procedures.

[]{#__RefHeading___Toc149980616 .anchor}Exhibit 5.53 -- CIS
Static/Dynamic Functionality Test Procedures

  --------------- -------------------------------------------------------------
  **Step Number** **Procedure**

  Static          
  Functionality   
  Check           

  1               Set Manifold to Proper Positions

  2               Start Data Recorder, Sample at 10 Hz

  3               Deflate RFS (or RFIT on trailer-only systems) tire 5 psi

  4               Flip Marker Switch when tire reaches 100 psi

  5               Stop Data Recorder

  6               Record File Name

  7               Repeat 8-14 but deflate in additional 5 psi increments until
                  tires reaches 75 psi on steer/60 psi on drive/trailer

  9               Start Data Recorder, Sample at 10 Hz

  10              Completely deflate RFS (or RFIT on trailer-only systems) to 0
                  psi

  11              Flip Marker Switch when tire reaches 100 psi

  12              Stop Data Recorder

  13              Record File Name

  Dynamic         
  Functionality   
  Check           

  14              Set all tires to Cold Inflation Pressure (CIP=105 psi)

  15              Deflate RFS (or RFIT on trailer-only systems) tire 5 psi

  16              Drive vehicle at 45 mph for 10 minutes (1 lap) around HST

  17              Flip Marker Switch when tire reaches 105 psi

  18              Stop Data Recorder

  19              Record File Name

  20              Repeat 14-19 but deflate in additional 5 psi increments until
                  tires reaches 75 psi on steer/60 psi on drive/trailer

  21              Repeat 1-20 for LFOD and RTAG (or LROT on trailer-only
                  systems)
  --------------- -------------------------------------------------------------

Exhibit 5.54 summarizes the Vigia CIS static functionality test data.
The system inflated all tires to target pressures over a wide range in
time; the longest time required was less than 8 minutes with some tires
requiring well under a minute. The data is seemingly scattered due to
the effect of the air system/compressor supplying the air reservoirs on
the vehicle. During static testing, "shop air" was used to reduce the
variability of the engine-driven compressor output pressure cycles.
However, the shop compressor duty cycle was also somewhat variable. The
inflation systems inflated tires much faster during the periods when the
compressor was charging the system.

[]{#__RefHeading___Toc149980617 .anchor}Exhibit 5.54 -- Vigia CIS Static
Functionality Test Data

  ----------------- --------------------------- --------------------------
  **Tire Set**      **Initial Pressure (psi)**  **Final Pressure (psi)**

  RFS/Steer Axle                                

                    100                         102

                    95                          103

                    90                          103

                    85                          103

                    80                          103

                    75                          103

                    0                           103

  LFOD/Drive Axle                               

                    100                         106

                    95                          105

                    90                          105

                    85                          106

                    80                          106

                    75                          106

                    70                          107

                    65                          106

                    60                          104

  RTAG/Tag Axle                                 

                    100                         106

                    95                          106

                    90                          106

                    85                          107

                    80                          107

                    75                          107

                    70                          107

                    65                          108

                    60                          108
  ----------------- --------------------------- --------------------------

Exhibit 5.55 displays the inflation times for the Vigia CIS used on the
RTAG tire for a range of initial tire pressures. These rates are typical
of the static test of the other tire positions. In general, it takes
longer to inflate tires from lower initial pressures; however, the
reservoir pressure has a large effect on the inflation rates as
discussed above. Also the pressures rises very quickly at the beginning
of the inflation test due to the need to tee in the pressure transducer
on the system fill line because of the system's use of its own rotary
union. This location of the transducer shows a pressure that starts at 0
psi and an artificially high pressure in the early portion of the
inflation test because it is actually measuring the fill line pressure
during inflation. All of the tests appear to reach or nearly reach the
target inflation pressures within 3 minutes or less.

[]{#__RefHeading___Toc149980618 .anchor}Exhibit 5.55 -- Vigia CIS RTAG
Static Functionality Test

![](media/image64.wmf){width="6.585416666666666in"
height="4.042361111111111in"}

Exhibit 5.56 summarizes the Vigia CIS dynamic functionality test data.
The data show that the system is capable of inflating tires from
pressures ranging down to 40 psi below the target inflation pressure of
approximately 105 psi in several minutes or less. Again, there is
tremendous variability in the inflation rates due to the cycling of the
vehicle compressor, primary reservoir, and secondary reservoir pressures
so that the resulting inflation times did not reflect the initial
starting pressures. The RFS tire was not tested below 80 psi while
driving on the test track for safety reasons.

[]{#__RefHeading___Toc149980619 .anchor}Exhibit 5.56 -- Vigia CIS
Dynamic Functionality Test Data

  ------------------------------------------------------------------------
  **Tire Set**      **Initial Pressure (psi)**  **Final Pressure (psi)**
  ----------------- --------------------------- --------------------------
  RFS/Steer Axle                                

                    100                         103

                    95                          103

                    90                          103

                    85                          103

                    80                          103

  LFOD/Drive Axle                               

                    100                         108

                    95                          108

                    90                          108

                    85                          108

                    80                          108

                    75                          108

                    70                          104

                    65                          104

                    60                          104

  RTAG/Tag Axle                                 

                    100                         102

                    95                          105

                    90                          105

                    85                          105

                    80                          105

                    75                          104

                    70                          104

                    65                          104

                    60                          104
  ------------------------------------------------------------------------

Exhibit 5.57 displays the test data from the Vigia CIS dynamic
functionality test. The data show that the system is capable of
inflating all tires from pressures ranging from 45 psi below the target
pressure of 105 psi within a few minutes and at times considerably less.
Again, the data show a high degree of variability due to the vehicle's
compressor loading cycles.

[]{#__RefHeading___Toc149980620 .anchor}Exhibit 5.57 -- Vigia CIS LFOD
Dynamic Functionality Test

![](media/image65.wmf){width="6.585416666666666in"
height="4.042361111111111in"}

Exhibit 5.58 shows the static functionality test of the PSI CIS.

[]{#__RefHeading___Toc149980621 .anchor}Exhibit 5.58 -- Static
Functionality Test of PSI CIS

![](media/image66.wmf){width="6.585416666666666in"
height="4.042361111111111in"}

As shown in Exhibit 5.58, the PSI CIS inflates under-inflated tires
(from 85, 75, and 65 psi) up to 94 to 95 psi, which was the system
pressure set by the manufacturer's installers who outfitted the test
trailer. This is as expected based upon the intended functionality of
the system and the system pressure setting set by the manufacturer. The
same test series was performed for this system on the RFIT tire, which
exhibited similar results within a 2- to 3-psi range, as shown in
Exhibit 5.59.

[]{#__RefHeading___Toc149980622 .anchor}Exhibit 5.59 -- Static
Functionality Test Results for PSI CIS

+----------------------+-----------------------+-----------------------+
| **CIS #1 --          |                       |                       |
| Trailer-Only**       |                       |                       |
+----------------------+-----------------------+-----------------------+
| **Tire Set**         | **Initial Pressure**  | **Final Pressure      |
|                      |                       | (psi)**               |
|                      | **(psi)**             |                       |
+----------------------+-----------------------+-----------------------+
| RFIT                 | 86                    | 93                    |
+----------------------+-----------------------+-----------------------+
| RFIT                 | 76                    | 93                    |
+----------------------+-----------------------+-----------------------+
| RFIT                 | 68                    | 93                    |
+----------------------+-----------------------+-----------------------+
| RFIT                 | 63                    | 92                    |
+----------------------+-----------------------+-----------------------+
| LROT                 | 85                    | 95                    |
+----------------------+-----------------------+-----------------------+
| LROT                 | 76                    | 94                    |
+----------------------+-----------------------+-----------------------+
| LROT                 | 66                    | 94                    |
+----------------------+-----------------------+-----------------------+

Exhibit 5.60 shows the results of the dynamic functional test performed
on the PSI CIS.

[]{#__RefHeading___Toc149980623 .anchor}Exhibit 5.60 -- Dynamic
Functionality Test of PSI CIS

![](media/image67.wmf){width="6.585416666666666in"
height="4.049305555555556in"}

As shown in Exhibit 5.60, the PSI CIS performed similarly under the
dynamic test as it did under the static test---inflating tires (from 86,
73, 63 psi) up to 93 to 95 psi. The spikes in the LROT-65 trace are due
to noise in the data. These same test series were performed on the RFIT
tire, which experienced similar test results as shown in Exhibit 5.61.

[]{#__RefHeading___Toc149980624 .anchor}Exhibit 5.61 -- Dynamic
Functionality Test Results for PSI CIS

+----------------------+-----------------------+-----------------------+
| **CIS #1 --          |                       |                       |
| Trailer-Only**       |                       |                       |
+----------------------+-----------------------+-----------------------+
| **Tire Set**         | **Initial Pressure**  | **Final Pressure      |
|                      |                       | (psi)**               |
|                      | **(psi)**             |                       |
+----------------------+-----------------------+-----------------------+
| RFIT                 | 86                    | 94                    |
+----------------------+-----------------------+-----------------------+
| RFIT                 | 76                    | 93                    |
+----------------------+-----------------------+-----------------------+
| RFIT                 | 70                    | 92                    |
+----------------------+-----------------------+-----------------------+
| RFIT                 | 58                    | 91                    |
+----------------------+-----------------------+-----------------------+
| LROT                 | 86                    | 93                    |
+----------------------+-----------------------+-----------------------+
| LROT                 | 73                    | 93                    |
+----------------------+-----------------------+-----------------------+
| LROT                 | 65                    | 95                    |
+----------------------+-----------------------+-----------------------+
| LROT                 | 56                    | 94                    |
+----------------------+-----------------------+-----------------------+

Exhibits 5.58 through 5.61 show that the PSI CIS responded as expected
to under-inflated tires from 85 to 56 psi, inflating them to within 2 to
3 psi of the targeted 95 psi.

### Threshold Warning Level Tests

The threshold warning tests for CIS evaluates their ability to continue
to inflate a tire with a constant leak and determine the level when a
low tire pressure warning is given. The systems are also tested for
their ability to isolate intact tires from failed tires. The systems
were tested both statically to determine basic functionality and
dynamically at 45 mph to determine the effect of the vehicle operation
on the inflation system performance. The inflation system threshold
warning test procedures are detailed in Exhibit 5.62.

[]{#__RefHeading___Toc149980625 .anchor}Exhibit 5.62 -- CIS Threshold
Warning Test Procedures

  ----------- -------------------------------------------------------------
  **Step      **Procedure**
  Number**    

  Threshold   
  Warning     
  Level       

  1           1 Set all tires to Cold Inflation Pressure (CIP=100 psi)

  2           Set Manifold to Proper Positions

  3           Start Data Recorder, Sample at 10 Hz

  4           Initiate slowly leaking RFS (or RFIT on trailer-only systems)
              tire pressure at a rate of approximately 1.5 psi/min\*

  5           Drive vehicle at 45 mph for 10 minutes (1 lap)

  6           Flip Marker Switch when system indicates low tire pressure

  7           If no warning observed after 1 lap, increase leak rate by
              approximately 0.5 psi/min\*

  8           Repeat 5-7 until low pressure warning is observed

  9           Stop Data Recorder

  10          Record File Name

  11          Record Set Leak Rate

  12          Wait 30 minutes

  13          Repeat 1-12 for LFOD and RTAG (or LROT on trailer-only
              systems)
  ----------- -------------------------------------------------------------

Exhibit 5.63 displays a summary of the Vigia CIS threshold warning data.
The system provides a warning almost immediately after the start of the
leak. The system was able to keep up with a constant leak rate of 1.5
psi/minute. The system experienced a continued loss of tire pressure
during the testing period with a 5-psi-per-minute leak, but may be able
to continue over a longer period and stabilize at a slightly lower
pressure. Ultimately, the size and duty cycle of the vehicle's
compressor and air system determine the maximum sustainable leakage
rate.

[]{#__RefHeading___Toc149980626 .anchor}Exhibit 5.63 -- Vigia CIS
Threshold Warning Test (45 mph) Data

+--------+---------------+----------------------+----------+---------+
| **Tire | **Initial     | **Final Pressure**   | **Leak   | **Wa    |
| Set**  | Pressure**    |                      | Rate**   | rning** |
|        |               | **(psi)**            |          |         |
|        | **(psi)**     |                      | **(ps    | **(Ye   |
|        |               |                      | i/min)** | s/No)** |
+--------+---------------+----------------------+----------+---------+
| RFS    |               |                      |          |         |
| /Steer |               |                      |          |         |
| Axle   |               |                      |          |         |
+--------+---------------+----------------------+----------+---------+
|        | 106           | 106                  | 1.5      | Yes     |
+--------+---------------+----------------------+----------+---------+
|        | 108           | Continued pressure   | 5        | Yes     |
|        |               | loss                 |          |         |
+--------+---------------+----------------------+----------+---------+
| LFOD   |               |                      |          |         |
| /Drive |               |                      |          |         |
| Axle   |               |                      |          |         |
+--------+---------------+----------------------+----------+---------+
|        | 103           | 103                  | 1.5      | Yes     |
+--------+---------------+----------------------+----------+---------+
|        | 104           | Continued pressure   | 5        | Yes     |
|        |               | loss                 |          |         |
+--------+---------------+----------------------+----------+---------+
| RT     |               |                      |          |         |
| AG/Tag |               |                      |          |         |
| Axle   |               |                      |          |         |
+--------+---------------+----------------------+----------+---------+
|        | 104           | 104                  | 1.5      | Yes     |
+--------+---------------+----------------------+----------+---------+
|        | 104           | Continued pressure   | 5        | Yes     |
|        |               | loss                 |          |         |
+--------+---------------+----------------------+----------+---------+

Exhibit 5.64 displays the data from the Vigia CIS threshold warning test
of the RFS tire. The system shows its ability to maintain tire pressure
with a 1.5-psi-per-minute leak rate as evidenced by the 1.5 psi trace.
With a leak rate of 1.5-psi-per-minute, the RFS tire pressure drops over
time from 106 psi to about 104 psi. The inflation system then begins to
fill the tire as evidenced by the trace oscillating as the system cycles
its inflation valve open and closed. Over the period of the test with a
5-psi-per-minute leak, the RFS tire continuously lost pressure as
evidenced by the 5-psi-per-minute trace dropping steadily from 108 psi
to 92 psi over the 500 seconds of the test. The inflation system cycled
briefly at the beginning of the 5-psi-per-minute leak and then left the
inflation valve open. During the 5-psi-per-minute leak, the vehicle
compressor did not load and charge the reservoir, which would have
allowed some level of recovery of the RFS tire pressure. The yellow
warning light was illuminated, and the steer axle gauge indicated
below-target pressure from the start of the leaks.

[]{#__RefHeading___Toc149980627 .anchor}Exhibit 5.64 -- Vigia CIS RFS
Threshold Warning Test

![](media/image68.wmf){width="6.585416666666666in"
height="4.107638888888889in"}

Exhibit 5.65 shows the threshold warning level test of the PSI CIS.

[]{#__RefHeading___Toc149980628 .anchor}Exhibit 5.65 -- Threshold
Warning Level Test of PSI CIS

![](media/image69.wmf){width="6.585416666666666in"
height="4.016666666666667in"}

As shown in Exhibit 5.65, initial leak rates from 0.5 psi per minute to
10.0 psi per minute were set using the pressure control manifold, and
the vehicles were driven at 45 mph around the test track. The spikes in
the 1.0 psi/min trace are due to noise in the data. It should be noted
that an initial leak rate (psi/min) was set using the metering valve in
the control manifold, which yielded a fixed orifice size for the leak.
Therefore, as the pressure dropped, the leak rate decreased, shown by
the asymptotic graphs in Exhibit 5.65, as the rate reached a point at
which the inflation system could maintain the flow of air into and out
of the tire.[^18] Exhibit 5.66 shows complete results of the PSI CIS for
the test runs on the RFIT and LROT tires.

[]{#__RefHeading___Toc149980629 .anchor}Exhibit 5.66 -- Threshold
Warning Test Results for PSI CIS

+----------------+-----------------+-----------------+-----------------+
| **CIS #1 --    |                 |                 |                 |
| Trailer-Only** |                 |                 |                 |
+================+=================+=================+=================+
| **Tire Set**   | **Leak Rate**   | **Initial       | **Final         |
|                |                 | Pressure**      | Pressure        |
|                | **(psi/min)**   |                 | (psi)**         |
|                |                 | **(psi)**       |                 |
+----------------+-----------------+-----------------+-----------------+
| RFIT           | 0.5             | 100             | 99              |
+----------------+-----------------+-----------------+-----------------+
| RFIT           | 1.0             | 100             | 92              |
+----------------+-----------------+-----------------+-----------------+
| RFIT           | 1.5             | 100             | 90              |
+----------------+-----------------+-----------------+-----------------+
| RFIT           | 2.5             | 101             | 86              |
+----------------+-----------------+-----------------+-----------------+
| RFIT           | 5.0             | 101             | 79              |
+----------------+-----------------+-----------------+-----------------+
| RFIT           | 10.0            | 100             | 55              |
+----------------+-----------------+-----------------+-----------------+
| LROT           | 1.5             | 100             | 92              |
+----------------+-----------------+-----------------+-----------------+
| LROT           | 2.5             | 100             | 90              |
+----------------+-----------------+-----------------+-----------------+
| LROT           | 5.0             | 101             | 81              |
+----------------+-----------------+-----------------+-----------------+
| LROT           | 10.0            | 100             | 64              |
+----------------+-----------------+-----------------+-----------------+

In general, the results in Exhibit 5.66 show that the PSI CIS is capable
of supplying air to refill the trailer tires, but a leak orifice that
has an initial leak rate of more than 0.5 psi/min results in a lower
sustained tire pressure than the system's set pressure. An initial leak
rate above 5.0 psi per minute yields a sustained final tire pressure of
20 psi below target---considered a serious under-inflation issue.

### Loaded Test at High Speed

The loaded dynamic tests at high speed for central inflation systems
evaluate their ability to continue to inflate a tire with a constant
leak and determine the level when a low tire pressure warning is given.
The systems are also tested for their ability to isolate intact tires
from failed tires. The systems were tested at the vehicle's gross
vehicle weight rating and at 75 mph to determine the effect of the
vehicle operation on the inflation system performance. Exhibit 5.67
details the procedures for the inflation system loaded dynamic test at
high speed.

[]{#__RefHeading___Toc149980630 .anchor}Exhibit 5.67 -- CIS Loaded
Dynamic Test at High-Speed Test Procedures

  ---------- -------------------------------------------------------------
  **Step     **Procedure**
  Number**   

  Loaded     
  Test at    
  High Speed 

  1          Set all tires to Cold Inflation Pressure (CIP=105 psi)

  2          Set Manifold to Proper Positions

  3          Start Data Recorder, Sample at 10 Hz

  4          Begin leaking RFS tire at the threshold rate determined in
             Test #1

  5          Drive the vehicle at 45 mph for 10 minutes (1 lap) around HST

  6          Flip Marker Switch when system indicates low tire pressure

  7          If no warning observed, stop vehicle, increase leak rate by
             an additional 0.5 psi/min, Repeat 5-6

  8          Drive vehicle at 75 mph for 22.5 miles (3 laps) around HST

  9          Flip Marker Switch when low pressure warning is extinguished

  10         If the low tire pressure warning is maintained, repeat 8-9
             once.

  11         If the low tire pressure warning is maintained, stop vehicle,
             wait until tire reaches CIP

  12         Drive vehicle at 45 mph for 10 minutes (1 lap) or until
             warning indicator is extinguished

  13         Stop Data Recorder

  14         Record File Name

  15         Wait 30 minutes

  16         Repeat 1-15 for LFOD and RTAG
  ---------- -------------------------------------------------------------

The Vigia CIS is limited more by the compressor and air system on the
vehicle than the inflation system components. The system sensor is
sensitive to 2 to 3 psi for activation. The maximum tire leakage rate
that can be accommodated is typically 5 to 8 psi per minute, with 120 to
140 psi pressure in the reservoir tank. With this rate of leakage, the
pressure on the lines/tires will be maintained at 96 to 105 psi. Exhibit
5.68 is a summary of the data for the Vigia CIS loaded test at high
speed. The data show that the system can re-inflate the tires back to
the target pressure of 105 psi with leakage rates of 5 to 6 psi per
minute. However, the tires do not maintain 105 psi, and cycle up and
down with the vehicle air compressor loading cycles. The test of the
LFOD/Drive Axle did not have a compressor cycle during the test time
period, and the system was not able to re-inflate the tire until after
the test when the compressor loaded.

[]{#__RefHeading___Toc149980631 .anchor}Exhibit 5.68 -- Vigia CIS Loaded
Test at High Speed (75 mph) Data

+-------------+------------+-----------------------------+------------+
| **Tire      | **Initial  | **Peak Recovery Pressure**  | **Leak     |
| Set**       | Pressure** |                             | Rate       |
|             |            | **(psi)**                   | (          |
|             | **(psi)**  |                             | psi/min)** |
+-------------+------------+-----------------------------+------------+
| RFS/Steer   | 105        | 105                         | 5          |
| Axle        |            |                             |            |
+-------------+------------+-----------------------------+------------+
| LFOD/Drive  | 105        | 93 (compressor did not load | 6          |
| Axle        |            |                             |            |
|             |            | during test.)               |            |
+-------------+------------+-----------------------------+------------+
| RTAG/Tag    | 105        | 105                         | 6          |
| Axle        |            |                             |            |
+-------------+------------+-----------------------------+------------+

Exhibit 5.69 displays the data from the test of Vigia CIS RTAG tire
loaded at high speed. The exhibit shows that the system is able to
re-inflate the RTAG tire back to its initial pressure of 105 psi, but
the tire only reached the target pressure during periods of compressor
loading, as evidenced by the traces of the primary and secondary
reservoirs. During the test period, as the vehicle was operating at 75
mph, the compressor cycled on and off as the trace for the secondary
reservoir pressure increased and decreased. The inflation system is
connected to the secondary reservoir that supplies the front brakes to
isolate the primary reservoir that supplies the rear brakes, which
provide most of the braking force of the vehicle. Interestingly, as the
test progressed, the system maintained the target inflation pressure for
shorter durations. This appears to be due to the interaction of the
primary and secondary air reservoir pressure switches and the control
logic that cycles the compressor loading.

[]{#__RefHeading___Toc149980632 .anchor}Exhibit 5.69 -- Vigia CIS RTAG
Loaded High-Speed Test with Rapid Leak

![](media/image70.wmf){width="6.585416666666666in"
height="3.977777777777778in"}

The PSI CIS installed in the test trailer had a malfunctioning warning
indicator light. The cause of the fault could not be determined by the
manufacturer representative on site; therefore, no loaded test at
high-speed procedures was performed on the PSI CIS.

### Failure Modes Test

The failure modes test for CIS primarily evaluates the potential of a
large air leak to deplete the air brake system reservoir. The failure
modes test also determines whether an air leak will cause the system to
run constantly without giving the driver a warning of a flat tire.
Finally, the failure modes where tires are interconnected are
investigated to ensure that loss of inflation pressure in a single tire
does not affect the interconnected tires. Exhibit 5.70 details the CIS
failure modes test procedures.

[]{#__RefHeading___Toc149980633 .anchor}Exhibit 5.70 -- Failure Modes
Test Procedures

  ------------------------------------------------------------------------
  **Step     **Procedure**
  Number**   
  ---------- -------------------------------------------------------------
  Failure    
  Modes      

  1          Set all tires to Cold Inflation Pressure (CIP=105 psi)

  2          Set Manifold to Proper Positions

  3          Start Data Recorder, Sample at 10 Hz

  4          Perform 5 brake stops (60 to 0 mph @ max deceleration rate)

  5          Initiate rapidly leaking RFS (or RFIT on trailer-only
             systems) tire at a rate of approximately 6 psi/min\*

  6          Perform 10 braking stops from 40 to 20 mph @ 10 ft/sec^2^,
             every mile

  7          Flip Marker Switch when system indicates low tire pressure

  8          Perform 5 brake stops (60 to 0 mph @ max deceleration rate)

  9          Stop Data Recorder

  10         Record File Name

  11         Wait 30 minutes

  12         Repeat 1-11 for LFOD and RTAG (or LROT on trailer-only
             systems)
  ------------------------------------------------------------------------

Exhibit 5.71 displays the data from the Vigia CIS RFS tire failure modes
test. The vehicle was put through a series of 5 brake snubs from 60 mph
to 0 mph and a 6 psi/minute leak was initiated, followed by 10 brake
snubs from 40 to 20 mph, followed by another 5 brake snubs from 60 to 0
mph. This placed a high level of stress on the braking system, and would
not be experienced in normal operations of the motorcoach. As indicated
by the traces for the primary and secondary reservoirs, the vehicle
compressor loaded twice during the test and maintained acceptable
pressure in the reservoirs for adequate braking performance. The RFS
tire pressure was also maintained by the inflation system as shown by
the RFS pressure trace. During the test, the warning light on the
console was illuminated when the system was inflating the tire, and the
pressure of the RFS tire was indicated on the steer axle gauge. The test
of the other tires on the vehicle yielded similar data.

[]{#__RefHeading___Toc149980634 .anchor}Exhibit 5.71 -- Vigia CIS RFS
Failure Modes Test

![](media/image71.wmf){width="6.566666666666666in"
height="4.003472222222222in"}

In Exhibit 5.72, the supply line between the control console on the
Vigia CIS and the secondary reservoir was cut to examine the potential
of a catastrophic failure of the system to drain the reservoirs of the
vehicle. Due to safety concerns, the vehicle was not driven for this
test. The trace for the primary reservoir remains constant, while the
secondary reservoir drains down to 83 psi where it is isolated by a
check valve from the inflation system. During this test, the red system
failure warning light illuminated and the gauges all read 0 psi. The
tires were all protected by check valves and remained at 105 psi.

[]{#__RefHeading___Toc149980635 .anchor}Exhibit 5.72 -- Vigia CIS
Failure Modes Test Total System Air Loss

![](media/image72.wmf){width="6.566666666666666in"
height="4.029861111111111in"}

Exhibit 5.73 shows a failure modes test of the PSI CIS.

[]{#__RefHeading___Toc149980636 .anchor}Exhibit 5.73 -- Failure Modes
Test of PSI CIS

![Exhibit 5.73 is a chart of the failure mode of the PSI CIS with a
rapid leak in the RFIT tire. The vehicle performed five braking stops
from 60 to 0 mph, then a leak was initiated in the RFIT tire at a rate
of 6 psi/min. A series of 10 braking snubs was performed from 45 to 20
mph, followed by another 5 braking stops from 60 to 0 mph. The rapid
leak rate resulted in a significant pressure drop in the RFIT. The
primary air reservoir maintained necessary air pressure for braking
throughout the test procedure---a consistent pattern for the period
before the leak and the period after the leak. The secondary air
reservoir showed a momentary loss of only 2 to 3 psi during the final
braking stops. ](media/image73.wmf){width="6.366141732283465in"
height="3.8736220472440945in"}

In the test shown in Exhibit 5.73, the vehicle performed five braking
stops from 60 to 0 mph, then a leak was initiated in the RFIT tire at a
rate of 6 psi/min. A series of 10 braking snubs was performed from 45 to
20 mph, followed by another 5 braking stops from 60 to 0 mph. As shown
in Exhibit 5.73, the rapid leak rate resulted in a significant pressure
drop in the RFIT despite the presence of the CIS. The low pressure
ultimately resulted in the test engineer needing to terminate the leak
once pressure reached 45 psi.

Exhibit 5.73 shows that the primary air reservoir maintained necessary
air pressure for braking throughout the test procedure---a consistent
pattern for the period before the leak and the period after the leak.
The secondary air reservoir showed a momentary loss of only 2 to 3 psi
during the final braking stops, but this was only temporary. The test
series performed on the LROT tire showed similar results to those in
Exhibit 5.73 in which no braking performance issues resulted from
operation of the CIS.

### Disablement Test

The disablement modes test determine whether the inflation system is
designed to provide a warning indicator if/when it is disabled and to
determine the ability of the system to protect the tire(s) from loss of
air pressure in the event of damage or failure of the system components.
Components of the system were purposely damaged or removed to simulate
damage or loss due to road debris, curb strikes, vandalism, etc. These
tests were performed statically due to safety issues related to tire
failures while driving the vehicle. Exhibit 5.74 details the test
procedures for the disablement modes test.

[]{#__RefHeading___Toc149980637 .anchor}Exhibit 5.74 -- CIS Disablement
Modes Test Procedures

  ---------------------------------------------------------------------------
  **Step        **Procedure**
  Number**      
  ------------- -------------------------------------------------------------
  Failure Modes 

  1             Set all tires to Cold Inflation Pressure (CIP=105 psi)

  2             Start Data Recorder, sample at 10 Hz

  3             Disable the TPMS according to disablement Mode #1

  4             Examine display, Take digital photo, Record Photo File Name

  5             Record response of system & if/when a warning/indicator of
                disablement is observed

  6             Stop Data Recorder

  7             Record file name

  8             Examine display, Take digital photo, Record Photo File Name

  9             Repeat 1-9 for each mode of disablement

  Possible      
  Modes of      
  Disablement   
  (Vigia CIS)   

  1             Disconnect hose from down line fitting, equivalent to cutting
                hose from console to down pipe

  2             Disconnect quick disconnect on down pipe

  3             Break rotor cover

  4             Cut rotor feed hose

  5             Disconnect down pipe

  6             Break rotor support

  7             Deflate LFOD to simulate flat/blowout with engine off to
                prevent inflation

  8             Repeat 7 but with engine running to attempt inflation of
                flat/blowout tire

  9             Disconnect hose at console

  Possible      
  Modes of      
  Disablement   
  (PSI CIS)     

  1             Detach LROT inflation hose on system-side; Attached cut
                replacement hose to system-side

  2             Detach LROT inflation hose on tire-side; Attached cut
                replacement hose to tire-side

  3             Fully open valve at output side of system box under trailer.

  4             Drill and Tap RFIT system hubcap, Inject with 100 psi shop
                air. Record if release vents (orange ring) open

  5             Cut hose leading from system box to trailer air reservoir
  ---------------------------------------------------------------------------

Vigia CIS Disablement Mode 1 was a condition where the hose from the
control console was disconnected from the down pipe fitting. The RFS and
LFS tires were protected by check valves; the console indicated no
pressure on the steer axle and the yellow warning light illuminated.
Exhibit 5.75 shows the physical damage to the system and the effect of
the severed supply line to the RFS down pipe (Mode 1).

[]{#__RefHeading___Toc149980638 .anchor}Exhibit 5.75 -- Vigia CIS
Disablement Mode 1 Test Inflation System #2

![](media/image74.png){width="3.479861111111111in"
height="2.629166666666667in"}

In Exhibit 5.76, the console reads 0 pressure on the steer axle, and the
instrument panel shows that the primary and secondary reservoirs were
also protected and retained pressure.

[]{#__RefHeading___Toc149980639 .anchor}Exhibit 5.76 -- Vigia CIS
Disablement Mode 1 Test System Console and Instrument Panel

![](media/image75.png){width="3.2534722222222223in"
height="2.4993055555555554in"}![](media/image76.png){width="3.2534722222222223in"
height="2.4993055555555554in"}

Vigia CIS Disablement Mode 2 differed from Mode 1 in that the quick
disconnect sealed off the line from the console. The hose check valve
protected the RFS tire from deflation. The system indicated normal
pressure in the LFS tire and functioned normally, but it could only
inflate the LFS tire.

Vigia CIS Disablement Mode 3 involved breaking the RFS rotor cover. The
rotor cover is cosmetic in nature and designed to break away to prevent
damage to the rotary union. The damage to the rotor cover had no effect
on the system.

Vigia CIS Disablement Mode 4 was a cut RFS rotor feed hose. This failure
was similar to Mode 1. The RFS and LFS tires were protected by check
valves, and the console indicated the steer axle had no pressure and the
yellow warning light illuminated. Exhibit 5.77 displays the damage in
Disablement Mode 4.

[]{#__RefHeading___Toc149980640 .anchor}Exhibit 5.77 -- Vigia CIS
Disablement Mode 4 Rotor Feed Hose Cut

![](media/image77.png){width="3.49375in" height="2.609027777777778in"}

Vigia CIS Disablement Mode 5 was, in effect, similar to Mode 2. The RFS
down pipe was disconnected from the system at the rotor and at the quick
disconnect. The RFS and LFS tires were protected by check valves, and
the RFS circuit was isolated from the system by the quick disconnect.
The console indicated 105 psi and functioned normally, but was only
monitoring the LFS tire.

Vigia CIS Disablement Mode 6 involved breaking the RFS rotor support.
The tire and the system were protected by the check valves. The RFS tire
remained at 105 psi, and the system console indicated 105 psi for the
steer axle.

Vigia CIS Disablement Mode 7 tested the system by setting a large leak
in the LFOD tire to simulate a flat or blow out. With the engine off to
prevent re-inflation of the LFOD tire, all of the air was dumped from
the LFOD tire. The system isolated all of the other tires on the vehicle
with check valves, and they remained at 105 psi.

Vigia CIS Disablement Mode 8 was similar to Mode 7, but with the engine
running. The compressor frequently cycled on to refill the secondary
reservoir as the tire continued leaking. The console indicated
approximately 60 psi as the system attempted to inflate the leaking tire
and the yellow warning light illuminated. All other tires on the vehicle
remained at 105 psi.

Vigia CIS Disablement Mode 9 entailed disconnecting the steer axle hose
at the console. The RFS and LFS tires were protected by check valves and
remained at 105 psi. The console indicated 0 psi on the steer axle, and
the yellow warning light illuminated.

Exhibit 5.78 provides a summary of the results for the Vigia CIS
disablement mode tests. In the disablement tests, the initial tire
pressures were recorded before the disablement procedure and after the
failure was created. The console gauge pressures for the affected
tire/axle were recorded after the failure to identify the different
system failure indications to the driver.

[]{#__RefHeading___Toc149980641 .anchor}Exhibit 5.78 -- Vigia CIS
Disablement Mode Test Results

  -------------------- ----------- -------------------- -----------------
  **Disablement Mode** **Initial   **Tire Pressure      **Console
                       Tire        (psi)**              Pressure (psi)**
                       Pressure                         
                       (psi)**                          

  Mode 1 (RFS)         105         105                  0

  Mode 2 (RFS)         105         105                  105

  Mode 3 (RFS)         105         105                  105

  Mode 4 (RFS)         105         105                  0

  Mode 5 (RFS)         105         105                  105

  Mode 6 (RFS)         105         105                  105

  Mode 7(LFOD)         105         0 (105 in all other  0/
                                   tires)               

  Mode 8 (LFOD)        105         0                    60

  Mode 9 (RFS)         105         105                  0
  -------------------- ----------- -------------------- -----------------

Exhibit 5.79 shows the disablement modes tested for the PSI CIS.

[]{#__RefHeading___Toc149980642 .anchor}Exhibit 5.79 -- PSI CIS
Disablement Results

  -------- -------------------- ----------------------- -------------------
  **PSI                                                 
  CIS**                                                 

  **Mode   **Purpose**          **Description**         **Result**
  \#**                                                  

  1        Simulate Failed      Detached LROT inflation System lost air
           Inflation Hose --    hose on system-side;    pressure, indicator
           System Perspective   Attached cut            light was
                                replacement hose to     illuminated, tire
                                system-side             and connected dual
                                                        was protected.

  2        Simulate Failed      Detached LROT inflation Tire lost air
           Inflation Hose --    hose on tire-side;      pressure, system
           Tire Perspective     Attached cut            and connected dual
                                replacement hose to     was protected from
                                tire-side               pressure loss.

  3        Simulate Failed      Fully open valve at     System lost
           output hose          output side of system   pressure, indicator
                                box under trailer.      light illuminated,
                                                        tires and air
                                                        reservoir were
                                                        protected from
                                                        pressure loss.

  4        Simulate Failed      Drill and tap RFIT      Release vents
           Internal Seal        system hubcap, Inject   opened properly to
                                with 100 psi shop air.  vent air.
                                Record if release vents 
                                (orange ring) open      

  5        Simulate failed      Cut hose leading from   Pressure protection
           input hose           system box to trailer   valve protected the
                                air reservoir           trailer air
                                                        reservoir.
  -------- -------------------- ----------------------- -------------------

Exhibit 5.79 shows that a failure of the fill hose located at the wheel
end resulted in a loss of air both in the affected tire and in the
system. However, the associated dual was protected from the failure, as
was the air reservoir. Failure of the internal seal in the hubcap
resulted in proper venting of system air by the pressure release vents.
Additionally, the pressure protection valve on the air reservoir
protected the reservoir against a failure in the inflation system or the
input hose.

### Operator Interface Evaluation

The operator interface for the Vigia CIS consists of a console with
three pressure gauges, three warning lights, a red system warning light,
and a green power light. Exhibit 5.80 shows the console unit of the
Vigia CIS. The only operator control is a power switch on the console.
If the air supply to the unit falls to 70 psi, the Vigia CIS
discontinues taking air from the tank, while the control panel flashes a
red light alerting the driver of a system problem. The gauges are read
directly by the driver and correspond to the pressure of the tires in
each axle.

[]{#__RefHeading___Toc149980643 .anchor}Exhibit 5.80 -- Vigia CIS
Operator Interface

![](media/image78.jpeg){width="2.779166666666667in"
height="1.5451388888888888in"}![](media/image79.jpeg){width="3.2069444444444444in"
height="1.56875in"}

When the system is adding air to a tire/axle, a yellow indicator light
flashes and an audible clicking sound is heard. If the system is
inflating a low tire, the yellow indicator light is on and the tire
pressure can be read from the gauge as it inflates. When the system is
within 3 psi of full inflation, it begins to turn on and off rapidly and
a series of clicks is heard until the calibrated pressure setting is
reached. The test drivers and mechanics commented that the console was
somewhat large, but the gauges were easy to read and the pressure
information was clearly presented. The combination of audible clicks and
flashing yellow lights effectively attracted the drivers' attention when
the system was active.

Exhibit 5.81 shows a photograph of the warning indicator for the PSI
CIS.

[]{#__RefHeading___Toc149980644 .anchor}Exhibit 5.81 -- Warning
Indicator for the PSI CIS

![](media/image80.jpeg){width="3.1694444444444443in"
height="1.1576388888888889in"}

As shown in Exhibit 5.81, the PSI CIS relies on a simple trailer-only
blue indicator light. The light should be mounted in such a way as to
allow the vehicle operator to see it through the left-side mirrors. In
the test setup, the indicator light did not function consistently and
the manufacturer representative present could not find the source of the
fault.

# OBSERVATIONS AND CONCLUSIONS

This chapter outlines the key observations and conclusions presented in
previous chapters regarding the performance and operational
characteristics of the various TPMS and their ability to detect tire
pressure abnormalities.

## Dual Tire Equalizers

Dual tire equalizers from two different manufacturers were installed on
the tractor-trailer test platform. Both units were installed on both
test vehicles without incident. Dual tire equalizers can be installed on
any vehicle with dual tires assemblies. Because the tractor-trailer had
eight dual tire sets as opposed to just two on the motorcoach, both of
the dual tire equalizer systems were installed on the tractor-trailer
for testing. This permitted more efficient use of test resources because
four axles on the tractor-trailer could be instrumented, as opposed to
only one axle on the motorcoach. The following are some key observations
and conclusions related to dual tire equalizers:

-   Dual tire equalizers are effective in balancing the pressures
    between the two tires. The equalization technologies function as
    designed under both static and dynamic conditions.

-   The two equalization systems were effective in isolating a tire with
    no leaks from an adjacent tire with a major leak. The isolation
    pressures vary with leakage rate and system characteristics. The two
    equalizer systems appear to have isolation pressures that are
    nominally set at about 80 psi. When exposed to a high pressure
    differential due to a high rate of leakage in one tire (e.g., from a
    severely damaged tire or a blowout), the equalizer systems tended to
    isolate the intact tire at higher pressures compared to slow leaks.

-   During disablement testing, cutting a hose to simulate damage from
    road debris resulted in a total loss of air from one dual, but the
    other tire was protected by a check valve. Simulated physical damage
    to the visual indicator/check valve assemblies of both units
    resulted in one system losing pressure in one tire, while the other
    system maintained pressure in both tires. Both systems prevented the
    loss of pressure in one or both tires in every failure mode
    implemented.

-   The two equalizers include a visual indicator that can provide a
    gross indication of tire pressure. They provide an indication that
    the tire pressure is within its target range; however, if the
    pressure falls below this range, they only show a "low" pressure
    condition and do not indicate the degree of under-inflation.

-   While the indicators provide a good visual indication of tire
    pressure, they can be difficult to read because they are mounted to
    the wheel and can become obscured by dirt.

## Tire Pressure Monitoring Systems

The team tested five different tire pressure monitoring systems for this
study project. They included two valve-stem-mounted, two wheel-mounted,
and one tire-mounted tire pressure monitoring system. The following are
some key observations and conclusions on the TPMS technology.

**General TPMS Observations**

-   The tire pressure monitoring systems tested in this project were
    generally accurate to within 2 to 3 psi from the values measured by
    the test instrumentation. In general, each system tested (valve-,
    wheel-, or tire-mounted) had the base-level functionality expected
    of their individual designs.

-   Low-pressure warning thresholds are "factory set" on some systems,
    but user-configurable on others. For those systems with factory
    settings, different warning levels ranging from 12 percent to 25
    percent below target pressure were observed. Further, all systems
    tested were generally within a 2- to 3-psi range of the expected
    warning threshold (whether set at the factory or by the user). The
    systems tested had similar performance both statically (vehicle not
    in motion) and dynamically (vehicle driven at 45 mph around the test
    track).

-   Many of the TPMSs tested used RF communications to transmit data
    between the sensors and the display unit or ECU. The relatively long
    length of typical CMVs means that additional on-board antennas are
    required for some of the systems to receive the sensor signals from
    trailer or tag axle tires. Disconnected or damaged antennas can lead
    to loss of signal from the sensors.

-   The operator interface for the TPMS tested varies significantly, but
    all used in-cab visual displays and audible alerts (except the
    tire-mounted TPMS) to warn the operator of inflation issues.

**Valve-Stem-Mounted TPMS Observations**

-   One of the systems tested initiated a warning when the pressure fell
    below a preset value (approximately 20 percent below target);
    however, the warning remained active until the tire was inflated to
    a higher value (approximately 15 percent below target). In other
    words, this system incorporates a "hysteresis effect" by having
    different pressure settings for when a warning is initiated versus
    when the warning is cancelled (or turned off).

-   Initially, it was thought that valve-stem-mounted technology
    typically does not compensate for increases in tire pressure as a
    result of increased tire temperature from high-speed driving.
    Therefore, as tire pressures increase due to increasing temperature,
    any low-pressure warnings that may have been active when the tire
    was cold would be cancelled as the tire temperature increased.
    However, the valve-stem-mounted technology tested on the motorcoach
    disproved this hypothesis during the testing and was shown to
    include temperature compensation. The manufacture used the
    hysteresis effect described above in conjunction with a proprietary
    algorithm to determine when tires are increasing pressure as a
    result of tire temperature.

-   Valve-stem-mounted systems are susceptible to loss and possibly
    theft because they have to be removed during wheel mounting and
    dismounting for vehicle maintenance and inspection. Reinstalling
    these systems on the proper wheel is also critical for maintaining
    the proper programming in the display units (swapped sensor
    locations lead to swapped sensor readings).

**Wheel-Mounted TPMS Observations**

-   An initial project hypothesis was that wheel-mounted technology
    included temperature compensation, and typically provided the best
    performance for correcting for tire temperature. However, during the
    high-speed testing, both wheel-mounted systems tested had active
    warnings cancelled when the pressure increased in the tire as a
    result of increased tire temperature. This occurred intermittently
    between the various test runs on different axles, although it
    appears from the test data that the systems were able to compensate
    for large increases in tire temperature (greater than 20 degrees F)
    a majority of the time, but smaller increases with corresponding
    pressure increases were not compensated for.

-   It was discovered during the TPMS installations that the
    wheel-mounted technologies are vulnerable to damage during tire
    mounting/demounting.

**Tire-Mounted TPMS Observations**

-   The tire-mounted technology tested included temperature
    compensation, which when read by the handheld reader, displayed
    temperature-corrected pressure along with the uncorrected pressure
    and the tire temperature.

-   The tire-mounted technology tested required handheld or gate reader
    devices to inspect tires---no in-cab display was available. In
    addition, the system was designed to provide an Internet-based tire
    maintenance and tracking database application hosted by the system
    manufacturer. This allowed data from the gate reader to be uploaded
    automatically to the Web database where a complete history of that
    tire/tire tag is stored. The handheld reader (used typically by
    maintenance personnel) could be docked with a cradle to upload scans
    of tire tags to the same Web database.

-   For the tire-mounted units, the gate reader clearance requirement
    dictated very slow vehicle speed, less than 5 mph. This limited the
    practical ability to test varying speeds through the gate reader.
    However, since the reader, according to the manufacturer, typically
    requires a 5- to 10-mph speed, the clearance is beneficial for the
    fleet in that it forces drivers to negotiate the gate reader slowly,
    thus ensuring complete reads of sensors.

## Central Inflation Systems (CIS)

CIS are available for motorcoaches, straight trucks, and tractor-trailer
vehicles. In this test, one system was tested on the motorcoach and one
was tested on the trailer of a tractor-trailer. The Vigia CIS used
externally routed air lines to each wheel end on the vehicle. The PSI
CIS used the hollow axles to route the air to the wheel ends. The
requirement of a rotary union for the Vigia CIS precluded the use of the
rotary union for the test instrumentation, somewhat limiting the range
of performance tests. Key observations and conclusions on the CIS
include the following:

-   The tested CIS generally perform as designed and specified by the
    manufacturer. The systems performed well in both static and dynamic
    conditions.

-   During the testing involving leak rates, the Vigia CIS was able to
    keep up with leak rates up to 5 to 8 psi/min. Ultimately, this
    system was limited by the vehicle's air compressor duty cycle and
    air system design.

-   Trailer-only systems use internal axle passages for supplying air to
    the wheel ends. This system kept most of the system components and
    lines out of sight and protected from potential damage.

-   The CIS tested on the trailer could maintain adequate tire pressure
    with slow leak rates (less than 1.0 psi/min), but would not maintain
    adequate tire pressure for higher leakage rates. This system
    appeared to be limited by its ability to flow air to the tires more
    than by the on-board compressor and air system.

-   During testing with heavy braking and simultaneous tire leaks, the
    vehicles' primary (rear brakes) and secondary (front brakes) air
    reservoirs did not become significantly depleted. The compressor had
    no difficulty recharging the reservoirs without having to run
    continuously. The test data suggests that the vehicles would likely
    have braking problems due to over-heating of the brakes before they
    would encounter problems with insufficient air pressure. During the
    tests, there were no adverse effects on braking performance observed
    with either CIS subjected to high leakage rates

-   Both CIS tested protected the "intact" tires from deflating if/when
    a catastrophic air leak was experienced in one of the other tires in
    the system. In this regard, the systems functioned in a manner
    similar to the dual tire equalizers' isolation circuits.

-   The PSI CIS used pressure release vents to protect the wheel hub
    from a failed internal seal. Without these vents, there is a
    potential to "blow out" the grease from the wheel end through the
    hub if an internal air seal fails in the axle. This type of failure
    would seriously damage the axle and could present a safety hazard.
    During the disablement modes tests (Section 5.3.5), the hubcap of a
    test axle was drilled to fit a shop air hose and 100 psi of shop air
    was applied to the hole simulating a failed internal seal. The PSI
    CIS vents in the hubcap properly opened releasing the pressurized
    air and preventing possible damage to the axle end and bearings. In
    a real failure of the internal seal, this could result in
    significant damage if there were no vents or if the vents failed to
    open as designed. While it is likely that this type of failure may
    not have an immediate safety impact, should the axle or bearings be
    damaged, handling of the vehicle might be compromised.

-   The Vigia CIS used an external rotary union assembly to provide air
    to the steer, drive, and tag axles. This exposed assembly could be
    prone to damage from road debris or impacts during CMV operations.
    The design of the trailer-only system (specifically, the use of the
    axle to deliver air pressure) prevents its application to drive and
    steer axles because they do not provide a hollow internal path to
    the wheel ends.

## General System Performance and Test Observations

Observations and conclusions about brake system performance and the
testing in general are as follows:

-   The central tire inflation pressure testing revealed an interaction
    between the high leakage rates and the vehicle air systems. High
    leakage rates cause increased compressor loading cycles resulting
    from the depletion of the secondary air reservoir by the CIS. The
    CIS are plumbed into the secondary reservoir to isolate the primary
    reservoir supply to the braking system. The primary air system
    supplies the rear brakes of the CMV, which provide the majority of
    the braking power of the vehicle. The secondary air reservoir
    supplies the front brakes of the vehicle, which require less air for
    operation and produce less braking power than the rear brakes.
    Vehicle air systems are not optimized to support a CIS with high
    leakage rates; therefore, the functionality of the CIS is often
    limited by the vehicle's air system. Additionally, there may be some
    long-term impact to the air system of the vehicle when exposed to a
    high leakage rate from the secondary reservoir including a
    significant increase in the duty cycle of the compressor and
    subsequent impacts on durability.

-   Installation time for systems vary, but in general
    valve-stem-mounted TPMS and dual tire equalizers were less time
    consuming to install, followed by wheel-mounted TPMS and
    tire-mounted TPMS, with CIS taking significant time for
    installation.

-   Temperature compensation in TPMS requires further refinement. During
    high-speed driving, the warning indicators would energize
    intermittently on some systems.

-   The Vigia CIS precluded the use of the custom rotary union that was
    used in the instrumentation set up for all the other systems tested.
    Future tests of CIS that incorporate rotary unions in their designs
    will need to use instrumentation such as wheel-mounted RF-type
    systems to transmit tire pressures and temperatures wirelessly to
    the data acquisition equipment. In the test of the Vigia CIS, the
    pressure transducers had to be plumbed into the pressure lines of
    the system being tested in order to monitor tire pressures. This is
    not an optimal condition as the pressure being measured is the
    inflation line pressure and not the tire pressure under conditions
    when there are high rates of inflation. The inability to use the
    instrumentation rotary unions also prevented the ability to monitor
    the tire temperatures via the installed thermocouples.

## Recommended Future Research

This project has provided comprehensive baseline assessments of a
variety of state-of-the-practice tire pressure monitoring and inflation
systems. The project team performed these assessments under controlled
test track conditions. Between test sequences, the team checked and
recalibrated various sensors and systems as needed. In the "real world"
of CMV operations, inspection and maintenance are generally performed at
much longer intervals---for CMVs operating in interstate commerce, the
mandatory periodic inspection interval is 12 months. Furthermore, the
useful operating life of a heavy-duty truck or motorcoach can be 10 to
12 years or longer, and the operating environment is much more severe
than on the test track. Therefore, there is a need to subject tire
pressure monitoring and maintenance sensors and systems to the rigors of
operation that a CMV would experience during the course of revenue
service.

An FMCSA-sponsored FOT involving the use of a transit bus fleet or
commercial trucking fleet would serve as a long-term test bed for new
equipment and maintenance practices. Data collected during the FOT could
be used to determine tire pressure monitoring and maintenance systems
ease of installation, ergonomics and functionality, accuracy and
sensitivity for detecting pressure changes, serviceability, reliability,
and overall customer acceptance. The utility of these systems could also
be evaluated with the help of the fleet operator to determine the
potential of using the systems for reducing maintenance costs,
increasing performance and safety, and reducing vehicle downtime for
scheduled or unscheduled maintenance and repair.

[]{#Appendix .anchor}APPENDIX A -- TIRE PRESSURE MONITORING AND
INFLATION SYSTEMS AND PRODUCTS

Dual Tire Pressure Equalizers

Tire pressure equalizers are designed to make tire pressure maintenance
a bit easier and equalize the pressure between two tires of a dual
assembly. Equalizing the tire pressure reduces irregular tire wear and
decreases rolling resistance, which improves fuel economy.

Tire pressure equalizer systems constantly monitor tire pressure and
equalize dual tire pressure by allowing air to transfer from one tire to
another as they run down the road. This is accomplished by the use of
two hoses that are plumbed to a check valve and each attached to the
valve stem of a dual tire. The check valve is attached to the hub. The
valve opens to allow airflow between the tires, but closes and shuts the
air off in case of an instantaneous air loss, which prevents both tires
from going flat. In a slow leak situation, the valve isolates both tires
after a pressure drop of approximately 10 psi. Since a central valve is
located in these devices, a single airing point is provided that
eliminates the need to remove the hoses to add air to the tires and
makes airing the tires easier since both tires in the assembly are aired
at the same time. These systems also provide a visual indicator of air
pressure conditions in the tires that can be seen from about 20 feet
away. They do not provide actual inflation pressures, but do provide
different types of go/no-go gauges that can indicate whether the tires
are under-inflated, over-inflated, or at the correct pressure. This
display feature is the primary difference between these systems.

One problem with tire pressure equalizers is that after a year or two
the accuracy of the valves deteriorates as the internal diaphragms wear.
Hose breakage is also a maintenance item.

**Link Manufacturing, Ltd.** produces the ***Cat's Eye Tire Pressure
Maintenance System***. The Cat's Eye Tire Gauge works in the same manner
as the Tire-Knight-S, but has a different display for inflation
condition. A 100-percent solid yellow display on the air valve indicates
that the tire pressure is +/- 2 percent of the recommended inflation
level. As the pressure drops, a vertical black line appears in the
center of the display. This is the "Cat's Eye." As pressure drops
further, the line widens until an all-black display indicates that tire
pressure is approximately 10 psi below the specified level. The display
is factory set for a specific pressure and is non-adjustable. This
system currently costs about \$50 an axle end with rubber hoses, and
\$60 an axle end with stainless steel hoses. The company has been
marketing the Cat's Eye Tire Pressure Maintenance System since 1990, and
has sold conservatively 125,000 units to date. It now sells
approximately 30,000 annually. *Link Manufacturing, Ltd., 223 15th
Street, N.E., Sioux Center, IA 51250-2120, (800) 222-6283, Pat Coghlan,
National Sales Director,
[[www.linkmfg.com]{.underline}](http://www.linkmfg.com/).*

**V-Tech International, Inc.** produces the ***Tire-Knight-S*** for
dual-truck tires. It is similar to other equalizer systems in that the
check valve assembly is mounted onto the wheel and the hoses are
attached to the valve stems of both dual tires. However, each tire is
connected to its own chamber and has its own valve for individual
inflating and pressure checking in the unit. A bypass connects and
equalizes the pressure in both tires when a piston opens or closes the
bypass. (The piston is the only moving part in the unit.) The piston
opens the bypass if both tires have a pressure greater than 85 to 90
psi. The piston closes the bypass if one tire blows out, one hose is
unhooked or cut, or both tires have a pressure of less than 80 to 85
psi. The position of the piston can be checked at a glance, although the
indicator is not very clear. The bypass is designed to allow minimal air
flow. In case of a leak, there will be a pressure difference between the
dual tires. Both tires would have to be gauged to determine which is
leaking. V-Tech is currently developing an integrated new
sensor/indicator that will produce a radio frequency (RF) or infrared
transmission signal (thus, improving upon V-Tech's current piston
indicator). The signal would be sent to a gate reader or in-cab monitor.
The prototype for this RF device will be available in June. V-Tech has
sold around 100 to 200 units locally in the Wisconsin area including
some to Schneider National. The price per unit is \$80, or \$640 for 16
positions. *V-Tech International, Inc., 227 Barbie Drive, West Bend, WI
53090, (262) 306-1708, Gottfried Hoffmann, President,
[[www.vtechint.com]{.underline}](http://www.vtechint.com/).*

Tire Pressure Monitoring Systems

There are several types of tire pressure monitors. These systems can be
categorized into the following types:

1.  Valve-Stem-Mounted Tire Pressure Monitors

2.  Wheel-Mounted Tire Pressure Monitors

3.  Tire-Mounted Tire Pressure Monitors

All of these systems monitor tire pressure through a device that senses
the pressure and forwards an RF signal to a display of some kind, which
is located in the tractor cab or in a more remote location. Many systems
also monitor temperature and convert the actual hot tire pressure to
cold pressure so that meaningful data is related to the user.

Valve-Stem-Mounted Tire Pressure Monitors

**Advantage PressurePro LLC** markets ***PressurePro*** (formerly Tire
Mate). The company began its entry into the tire pressure monitor market
in 1992 with Tire Mate, a product that fits over the valve stem like a
valve cap and transmits an RF signal indicating the tire pressure. The
product was not reliable, as it frequently failed to work in high
humidity and rainy conditions. It had a two-percent failure rate on the
sensors, and did not have the ability to notify users when it was not
functioning properly.

The company's newest product is called PressurePro. It is approximately
1 inch in diameter and ¾ inch in length, weighs 0.25 ounce, is
completely sealed, and fits over the valve stem. There is no RF
"cross-talk" between systems on adjacent wheels as each sensor signal is
uniquely identified by its own serial code. The sensors check tire
pressure every 15 seconds. The PressurePro system can monitor 1 to 34
tires with pressure from 10 to 150 psi. The receiver/monitor is battery
operated. The monitor is 6 inches wide by 3 inches tall and 0.5 inch
thick, and weighs just under 8 ounces. When tire pressure drops below
the low trigger pressure set by the user, the monitor triggers an alert
that displays tire location, low-pressure reading, and battery power in
the sensor. An audio and visual alert comes on when a tire is 10 percent
below target pressure, and a more aggressive alert identifies a tire
that is 20 percent below. The driver can scroll through the display to
check all tires on demand as well. The battery life in the valve-stem
sensors is expected to be 5 years in automobiles, 3 to 3 ½ years in RV
applications, and 2 years on commercial trucks. The life of the battery
is dependent upon mileage since the sensor is activated by tire
rotation. The RF signals from the trailer tires are linked to the
tractor receiver with a relay box that fits on the front of the trailer
and sends an RF signal to the cab. Alternatively, a handheld receiver
called the PressurePro Wand can read sensors within one foot of the
tire. A gate reader will be added to the product line as well.
PressurePro is currently being field tested. The company states that it
has 600 units installed on a variety of commercial vehicles. The cost
for an 18-wheel, tractor-trailer combination will be around \$1,075 for
the sensors and on-board receiver. Between 35,000 and 40,000 Tire Mate
units were sold primarily to the RV industry and owner operators.
Advantage has about 600 to 800 of the new PressurePro units operating on
commercial vehicles at this time. *Advantage PressurePro LLC, Inc., 205
Wall Street, Harrisonville, MO 64701, (800) 959-3505, Phil Zaroor,
President,
[[www.advantagepressurepro.com]{.underline}](http://www.advantagepressurepro.com/).*

The **AIR CHEX Equipment Co., Inc.** is developing the ***Air Chex***
system, which is a monitoring system that includes a pressure
sensor/transmitter, pressure gauge, valve stem, and connecting braided
hoses. The hose connects to the valve stem and has a pressure sensor
attached to the end. Air pressure is constantly monitored. The sensor
can be fitted with either a red LED that lights when the battery is low
or a buzzer that sounds on the wheel. A display is attached to the dash.
The Aero Disc is designed for dual wheels and has pressure gauges on the
disc face and valve stems. Behind the disc is the pressure
sensor/transmitter and connecting braided hoses to the valve stems. The
company claims the disc reduces turbulence around the wheel and improves
fuel economy by 4 percent. The cost of this system is projected to be
under \$30/wheel. *AIR CHEX Equipment Co., Inc. 27 New Street,
Nyack-on-Hudson, NY 10960, (845) 358-8179, Fax (845) 358-4804, Mark
Wallach, CEO.*

**Meritor WABCO** and **Michelin** developed the ***WABCO Integrated
Vehicle Tire Pressure Monitoring (IVTM) System*** for commercial
vehicles. Each tire and wheel assembly is equipped with a wheel module
that is attached to the outside of the wheel rim using two wheel bolts
and nuts. It is connected to the tire valves using pneumatic hoses. The
system checks pressure constantly and transmits tire pressure via an RF
signal every 15 minutes to the electronic control unit (ECU), and every
30 seconds in case of a significant pressure variation. Operating
frequency is 433 MHz. Power is supplied from a built-in lithium battery
with a five-year service life. The IVTM ECU is mounted on the vehicle
chassis attached equidistant between the front/rear axles and contains a
built-in antenna to receive the pressure data from all tires. This
location eliminates the need for additional antennas in the wheel
modules themselves. Trailers are equipped with their own
ECU/transmitter, which sends the tire inflation pressure RF signals to
the ECU on the tractor.

The dashboard display warns the driver optically and acoustically
whenever the inflation pressure of a tire on the tractor or trailer has
reached a critical value. A yellow lamp indicates a slight pressure
loss; a red lamp indicates a critical pressure loss. The position of the
concerned tire and its current inflation pressure can be queried on the
display at the push of a button. Under normal circumstances, there is no
pressure display as this system only displays exceptions. *WABCO GmbH,
Vehicle Control Systems, Am Lindener Hafen 21, D-30453, Hanover,
Postfach 91 21 62, Germany, 49-511-922-2144,
[[www.ivtm.com]{.underline}](http://www.ivtm.com/).*

The **Bigfoot Tire Alert Company** sells a pressure monitor system
called the ***Bigfoot Tire Alert*** that attaches large dial gauges to
the ends of the valve stems with hoses. The gauges are attached to the
outside of the wheels with the wheel studs. Adaptors are available for
hub piloted, stud piloted, and spoke wheel/demountable wheel systems.
Tire pressure is monitored by walking around the vehicle. The company
has been manufacturing and selling this product since June 2003 and has
sold approximately 450 units to date. The cost of the Bigfoot Tire Alert
is \$100 Canadian. The monitors are sold in packages of four. *Bigfoot
Tire-Alert Co., 4532 6th Street, N.E., Calgary, Alberta, Canada T2E 327,
(403) 276-7948,
[[www.bigfoot-tirealert.com]{.underline}](http://www.bigfoot-tirealert.com/).*

**Colorado Enterprise International** is developing a remote tire
pressure sensor for medium-duty trucks called the ***C.E.I. Tire
Monitor***. Its remote pressure sensor continually monitors the pressure
of each tire on a vehicle and provides the driver with a real-time
display of this information. The device is made up of two components.
The first is a small radio transmitter assembled into a modified tire
valve assembly. This valve is also equipped with a simple pressure
switch that is configured to activate at a predetermined threshold. Once
activated by low pressure, the transmitter will immediately transmit to
the unit on the dash the unique sensor identity code for that wheel
position. The unit on the dash will receive the code and match it
against the codes it has stored for the tires on that vehicle. If a
match is found, an enunciator will sound and an indicator will show
which wheel is generating the signal. A small standard lithium coin cell
battery that is estimated to provide more than 4 years of operation
powers the transmitter module. Once depleted, it can be replaced by the
user. (The company is exploring the possibility of powering the unit
with centrifugal force.) To provide notification of sensors that have
failed, are missing, or whose batteries have been depleted, the
transmitters are configured to periodically send a brief message to the
dash unit to confirm they are operational. If the dash unit does not
receive the periodic update, a different warning message is provided to
the driver. The company claims that the sensors attached to wheel
assemblies on doubles trailers can successfully transmit their signals
to the dashboard receiver. List price for this system is about \$500
(\$27/monitor) for an 18-wheeled vehicle. *Colorado Enterprise
International, 20 Lanning Blvd., Suite 215, East Windsor, NJ 08520,
(609) 918-9646, Edward Neefeldt, President.*

**Doran Manufacturing LLC** sells the ***Doran Tire Pressure Monitoring
System***. This system is made up of a sensor that screws onto the valve
stem of each tire and a receiver that fits into a standard gauge hole in
the dash. The sensors weight 25.7 grams and require the user to adjust
the pressure setting. The sensor comes apart to show a pressure scale
that has a range from 18 to 125 psi. The desired pressure is set using a
screwdriver. The sensor sends a "soft" alarm when the pressure drops to
10 percent below the setting and a more urgent audible alarm when the
pressure drops by 25 percent. Each sensor on the truck/tractor is marked
with the wheel position so that the system can tell the driver which
tire has low pressure. In addition, the system has unique codes for each
sensor so that trucks do not receive signals from each other in the
yard. However, all trailer sensors are coded the same, which allows for
drop and hook operations. Sensor batteries normally last 2 to 3 years
since the sensor only sends a signal when there is a low-pressure tire.
However, if no action is taken to correct the under-inflation condition,
the sensor sends the alarm continuously and the battery will last only
to 2 weeks. The receiver in the dash indicates which tire is low with a
graphic display. The appropriate position is indicated visually, a "Low
Tire" signal is shown, and an audio signal is heard. The receiver needs
three wires that attach to the battery, ignition, and ground. An antenna
is required to receive signals from trailer tire sensors. This antenna
is a wire that attaches to the back of the receiver and runs under the
cab to the back of the tractor. The Doran Tire Pressure Monitoring
System can monitor up to 34 tires. This product has been available since
January 2004. The price to equip an 18-wheel unit is around \$900 and a
6-wheel unit is \$300. The company anticipates that they will develop a
gate reader in the near future. Also available is the use of a
"Repeater" unit (like that used by Advantage PressurePro) that will send
the new codes for a new trailer hooked up to a tractor to the monitor so
it will recognize the new trailers sensors. *Doran Mfg., LLC, 2851
Massachusetts Avenue, Cincinnati, OH 45225, (866) 816-7233, Fax (513)
681-5604, [[www.doranmfg.com]{.underline}](http://www.doranmfg.com/).*

**Fleet Specialties Company** produces ***Tire Sentry*** for all classes
of trucks, buses, and RVs. Microchip wheel sensors attach to each valve
stem to continuously monitor tire pressure mechanically and transmit a
coded signal to the dash instrument when a loss of tire pressure is
detected. A warning light and audible alarm on the dash display shows
which tire is losing pressure. The Tire Sentry wheel sensors incorporate
a pressure sensor and a microchip transmitter powered by two standard
watch batteries and are set to the user's individual tire pressure
requirements. The user can change pressure settings when desired without
the need of special equipment. The wheel sensors that are installed on
each tire valve stem weigh less than 1 ounce and can transmit their
coded signal up to 50 feet to the antenna located near the drive axle of
the tractor. Tire Sentry's coding system prevents "cross-talk" to other
vehicles. The display module is wired into the vehicle's power source.
Tire Sentry's operating range is 50 feet. It operates on 303 or 418 MHz
frequency, has an air pressure range of 18 to 125 psi, and has a battery
life of two to three years. The cost of a Tire Sentry system for an
18-wheel vehicle is about \$750 to \$965 depending upon fleet size, and
for a 6-wheel bus is \$395 or less depending upon fleet size. Fleet
Specialties has been developing Tire Sentry since 1995 and has been
marketing it since 1997. It has sold "several thousand" units. *Fleet
Specialties Co., PO Box 4575, Thousand Oaks, CA 91361, (818) 889-1716,
Bill James or Bill Shore,
[[www.tiresentry.com]{.underline}](http://www.tiresentry.com/).*

**REA Technologies** has patented the ***Integrated Tire Pressure Audio
Alarm***. Although not yet on the market, this tire pressure warning
device consists of a long-life battery, a pressure sensing switch, and
an audio alarm. The device can be designed as either a discrete
thread-on (to an existing valve stem) unit or as a unit that would
completely replace a standard valve stem. Either design could be made
with a replaceable battery or as a throwaway unit after the battery is
completely drained. In the thread-on version, the device would simply
thread onto an existing valve stem, replacing the valve cap and
providing an intermittent audio warning, which could be heard within a
few feet of the device when a pre-determined, low-pressure threshold is
reached. The device is cylindrical, about 3/8 inch in diameter and
approximately one inch in length that essentially looks like a
valve-stem extension. The valve-stem version is designed to completely
replace the standard valve stem. This unit would perform just like a
standard valve stem except it provides the appropriate low-pressure
warning. Both units incorporate a small sensor/switch at its base and a
battery/sounder module. Since the units are under pressure, pressure is
constantly monitored. It does not have an in-cab display, but could
provide an LED display on the end of the valve stem. Depending on the
specific production model, pressure range, and features, the product is
priced at under \$10 per unit, or \$180 for a tractor-trailer
combination. *REA Technologies, Inc., 815 Brookmead Drive, O-Fallon, MO
63366, (636) 272-3770, Stephen Blakely, Director, Technology
Commercialization.*

**Sensatec, LLC** is developing a tire pressure and temperature sensor
system. The system alerts drivers to impending tire, bearing, and brake
problems by generating an audible, visual, and digital alert when any
increase in tire temperature or decrease in tire pressure occurs. It
provides constant monitoring of changes in tire pressure and temperature
on any vehicle. Tire Safe can be coupled to a satellite transmitter to
relay information to a central control facility. The system includes
sensors on each tire valve and a portable dash unit that consists of a
liquid-crystal display that is either battery powered, wired into the
vehicle's electrical system, or plugged into the cigarette lighter. The
tire sensor is a 1 x 2 inches cylinder that has a special universal
mounting sleeve, which allows it to fit on most valves stems. The
sensors are battery powered, and battery life is between 9 to 24 months
depending on battery type, frequency of interrogation, and amount of
use. The user can accept factory default conditions or program a variety
of performance monitoring features such as variable pressure,
temperature, frequency of reading, and alarm settings. The operator can
set the level at which the tire pressure and temperature measurements
will activate the audible and visual warning and alarm features. The
display unit continuously displays each tire's position and its
conditions. Green is normal, amber is a warning condition, and red is an
alarm condition. The display unit includes buttons for power and setup
menus and an optional computer connection for downloading of tire
condition history. A communication control relay box is available for
trailers that allows a single tractor to connect to any so equipped
trailer. The system operates on 900-950 MHz frequency. Market
introduction is expected in 2007. The price for the Tire Safe system
will be about \$1,200 for an 18-wheeled tractor-trailer unit and \$400
for a 6-wheeled bus. *Sensatec, LLC, 4 Woodbine Avenue, Greenwood Lake,
NY 10925, (845) 477-0200, Keith Yeates,
[[www.sensatecllc.com]{.underline}](http://www.sensatecllc.com/).*

**TireGuard** has a valve-stem-mounted tire pressure monitor called the
***TireGuard***. The valve cap-like monitor is available in pressure
ranges from 26 to 120 psi and as such is being marketed to the
automobile/light truck and motorcycle markets as well as the
recreational vehicle and commercial vehicle markets. The cost is \$7.50
per wheel retail with discounts being offered to fleets. A typical fleet
can equip all their wheels for around \$4/wheel or \$72 for an
18-wheeled tractor-trailer unit. This product has had problems with
leakage that causes tires to lose air and go flat, as experienced by the
author. *TireGuard, 1501 E. Orangethorpe Ave., Suite 170, Fullerton, CA
92831, (714) 773-4300, Fred Wiseman,
[[www.tireguard.net]{.underline}](http://www.tireguard.net/).*

Wheel-Mounted Tire Pressure Monitors

**Beru Group** introduced its ***Tire Safety System (TSS**)* as standard
OEM equipment for commercial vehicles in July 2003 in Europe. The TSS
consists of a central control unit and a set of battery-powered wheel
electronics attached to each wheel as well as a high frequency receiver
for each axle group. The sensors measure the tire pressure and
temperature at frequent intervals. These values are sent by radio
communications to the antennas where they are then converted into a
digital signal and sent to the central control unit for analysis. The
control unit analyzes the data, and converts tire air pressure to
standard pressure. The target tire pressure is set by the driver at the
press of a button or at the factory. Should a sudden drop in tire
pressure occur, a warning appears in the instrument panel display that
says "Flat tire, stop immediately." In the case of a slow loss of
pressure, a warning is displayed for the driver to increase the tire
pressure at the next opportunity, which is repeated each time the
ignition is turned on. This warning first appears when pressure has
dropped 6 psi. If the pressure falls 12 psi, the warning is displayed at
a higher urgency level in red instead of yellow. If the pressure loss
occurs when the vehicle is stationary, the driver is warned before he
starts his trip. The service life of the wheel electronics is 3 years,
and they operate at tire temperatures ranging from -40 to 120 degrees.
This system has been linked to satellite-aided telemetry in Europe. It
is understood that Beru has recently been talking to truck OEMs in the
United States. *Beru Group, Morikestr. 155, D-71636 Ludwigsburg,
Germany, 49- 7141-132- 233,
[[www.beru.com]{.underline}](http://www.beru.com/)*.

**HCI Corporation** sells the ***Tire-SafeGuard*** tire pressure
monitoring system. This system alerts drivers of low-pressure situations
by providing the location, temperature, and pressure readings via a
display unit and an audible signal. It monitors tire pressure
continuously with detection of abnormal tire pressure even while the
vehicle is parked. The Tire-SafeGuard product for commercial vehicles
(TPM-S206) uses a sensor mounted onto the wheel rim inside the tire. The
low-pressure and temperature warning is user adjustable and has a range
of 18 to 130 psi. The sensor transmitter automatically switches on when
the vehicle is moving faster than 15 mph and reports pressure readings
to the receiver using an RF signal. Pressure measurement accuracy is +/-
1 psi. The module has an operating temperature range of -40 to 250
degrees and a battery life of over 5 years. The receiver for the display
can be plugged into the auxiliary power outlet or can be directly
hardwired to the main power source. It is 3 ½ x 1 ^1^/~8~ x ^5^/~8~
inches in size and weighs 1.5 ounces. The cost to equip a tractor (10
positions) is \$650. The company has also developed a receiver to mount
onto trailers that will transmit signals from the trailer tires to the
in-cab monitor in the tractor. *HCI Corporation, 11245 E. 183rd Street,
Cerritos, CA 90703, (562) 926-7123 x 212, Tim Glassford, Sales Manager,
[[www.tiresafeguard.com]{.underline}](http://www.tiresafeguard.com/)*.

**SmarTire Systems, Inc**.'s currently marketed technology uses wireless
communications to monitor the air pressure and temperature in tires. A
small sensor is strapped on each wheel and collects temperature and
pressure data every 7 seconds. This data is transmitted via radio
frequency to a receiver display located inside the vehicle that
indicates individual tire pressure and temperature. The transmitted tire
data is captured by the receiver which in turn sends the information to
the display unit. The display unit allows the driver to toggle through
each wheel position and to select the type of information being
displayed: tire pressure, temperature, or pressure deviation. The
display incorporates a bright red LED light, which is activated whenever
a tire pressure irregularity is detected or when the temperature of a
tire goes above a preset level. SmarTire currently sells tire-monitoring
products for the RV market and for the CMV market. These products
monitor pressures up to 188 psi and accommodate up to 20 wheel
positions. *SmarTire Systems, Inc., Suite 150 -- 13151 Vanier Place,
Richmond, BC, Canada V6V 2J1, (604) 276-9884 x 308, John Bolegoh,
Product Manager,
[[www.smartire.com]{.underline}](http://www.smartire.com/).*

**Yokohama Tire Corp.** has also developed a chip technology for truck
and bus tires. Yokohama's has named its tire pressure monitoring system
***Hi-Technology Tire Engineering System (HiTES***). This system uses a
sensor that is mounted onto the tire rim and reports pressure and
temperature to a receiver and display unit in the cab of the truck.
Also, near the driver is an LED indicator that uses color changes to
show air pressure status. This allows drivers to confirm air pressure in
real time, reducing the time needed to conduct checks before they begin
a trip. Yokohama also has a handheld monitor. Data is automatically
transmitted to Yokohama's host computer where it is managed along with
information gained through periodic checks of tire wear, damage, and
distance traveled. This information can be analyzed and provided to the
customer via the Internet, enabling customers to precisely calculate the
appropriate times for tire changes and rotations. According to Yokohama,
it has been testing this technology in both OTR tires as well as medium
truck tires for several years. No price is yet available for this
system. HiTES was commercialized in Japan in July 2003 and is expected
to be marketed in limited quantities to trucking firms and bus companies
through Yokohama's tire sales subsidiaries throughout the world
including the United States. Yokohama is offering the system exclusively
to users of Yokohama tires. To date, the product has not been introduced
to the U.S. market. (One vehicle was equipped for test at the Port of
Tauranga, New Zealand in January 2004.) Yokohama plans to develop a
range of systems and products as part of its Tire Management System
program. *Yokohama Tire Corp., 1500 Indiana Avenue, PO Box 3250, Salem,
VA 24153, (540) 389-5426,
[[www.yokohamatire.com]{.underline}](http://www.yokohamatire.com/).*

Tire-Mounted Tire Pressure Monitors

**CrossLink, Inc.** was licensed by Bridgestone/Firestone to market the
***TreadLink*** system that is designed for trucks and other heavy
equipment vehicles, after 5 years of development. The TreadLink system
uses 1--inch, square, 915 MHz passive tags that have a read range of up
to

30 feet. Each tag holds 8 kilobits of data, including a unique serial
number, temperature and pressure readings, and the maximum temperature
of a tire during its lifetime. The pressure-sensing chip is permanently
installed on a patch inside the tire**.** The RFID transponder sends
data on the temperature-adjusted pressure of each vehicle's tires to
readers placed on the truck or at a terminal entrance or exit. These
readers are connected to PCs with special software to record the
information. Fleet operators can also scan the tags with a handheld
reader. The company says it is working on reusable tags as well as a
similar system that tracks tires and links them to the truck as part of
a larger vehicle-monitoring system. The TreadLink system will be
available in early 2004 for trucks, buses, tankers, trailers and
off-road heavy equipment vehicles over 6,000 pounds gross vehicle weight
rating. The tags are expected to be priced at around \$30 each. Fixed
readers will run about \$1,000. On-board and handheld readers will cost
about \$300 to \$400. *CrossLink,Inc., 6185 Arapahoe Avenue, Boulder, CO
80303, (303) 473-9232, Gary Zarlengo, President,
[[www.crosslinkinc.com]{.underline}](http://www.crosslinkinc.com/).*

**D.H. Products** is developing a tire pressure monitoring system called
the ***Flat Alert System*** that is placed inside the tire, although not
mounted to the tire. This system uses a silicone-covered,

2--inch, 2-ounce ball, which rolls inside the tire as the tire runs. It
has an expected life of 250,000 miles. A handheld reader is used to read
the pressure and a display/receiver is also located in the cab of the
vehicle. It is expected to retail at \$612 for an 18-wheeled unit (\$450
for fleets). *D.H. Products, 2231 Riviera Place, Longmont, CO 80501,
(303) 772-7902, Dusty Hill, President.*

**Michelin North America** introduced its **eTire** system for
medium-duty trucks in October 2002. The eTire system uses Michelin's
battery-less InTire Sensors that can be applied to any commercial truck
tire using the sidewall-mounted SensorDocks, which are molded rubber
pieces that chemically cure to the inside of the sidewalls in the same
fashion as tire repair units. The sensor unit slips over a knob on the
rubber dock and locks into place. Once installed, the sensors remain
throughout the entire life of the tire including retread processes. The
sensor is removable and can be reattached to a new truck tire with a new
SensorDock. The sensors measure temperature and pressure on demand and
communicate this information along with wheel position, and a
programmable identification number for its respective tire, to drive-by
and handheld readers that power the sensors. Other sensors located on
the tractor and trailer provide vehicle identification information at
the same time. The sensors include an RF transmitter, pressure and
temperature sensors, and an antenna, which are encased in impact- and
heat-resistant plastic. The unit measures 4 x 1.5 inches and weighs less
than an ounce. The vehicle must be traveling about 5 mph or less past a
gate reader for the reader to receive the information from all the tires
including the inside duals. The reader picks up about 95 percent of the
sensor information when a vehicle drives by. The sensors included
temperature compensation. The information gathered is reported in a
fleet specific manner via an Internet server to Michelin's BIBTRACK Web
site, which is home to BIBTRACK software that tracks tires and provides
recommended actions for problem tires. Fleets can get up-to-date
information on their tires, track tire costs, and monitor inventories
around the clock by going on-line. No data is stored on the sensors
themselves. This system does not have an in-cab display. The InTire
Sensors do not have 360-degree read capability, so the handheld reader
must be positioned over the sensor to read it. Michelin has an eTire
label installed on the outside of the tire that visually locates the
sensor. Each sensor unit costs about \$30, but actual fleet cost will
vary based on fleet size. Handheld readers are approximately \$6,000,
and gate readers are approximately \$10,000 to \$12,000. No unit sales
numbers are available. *Michelin North America Inc., PO Box 19011,
Greenville, SC 29602, (864) 458-5476, Randy Clark, Vice President of
Marketing, Truck Tire Unit,
[[www.michelintruck.com]{.underline}](http://www.michelintruck.com/).*

Tire Pressure Maintenance Systems

There are basically two types of tire inflation systems. The first type
uses air from the vehicle's air system to inflate the vehicle's tires.
These systems are generally referred to as central tire inflation
systems. The second type uses a pump of some kind that is separate from
the vehicle's air system to generate air. These systems are referred to
as continuous tire pressure pumps.

Central tire inflation systems take the air that is stored in the air
brake wet tanks on a vehicle and use it to supply air to the tires. This
can be done on demand or automatically triggered through sensors that
monitor tire pressure. These systems can be broken down into two
types---constant and variable. Constant systems maintain tire pressure
at a single preset level. They eliminate the need to check tire pressure
manually and allow a vehicle to remain in-service despite small air
leaks in one or more of its tires. Constant tire inflation systems have
no involvement from the driver. They automatically sense the pressure in
the tires and inflate as necessary when they lose air. A drawback to
these systems is that the external hoses can get damaged and render the
systems ineffective and may even deflate tires. Seal life in the axle
ends of systems under contact pressure is reduced. Also, tires with
undetected nail holes can develop separations over time.

Variable central tire inflation systems can raise or lower tire
pressures during vehicle operation to compensate for varying load and
road conditions in addition to maintaining tire pressure. These systems
allow the driver to interact with the system and change tire pressure on
demand. They are expensive and are usually used for on-off road
operations such as logging, construction, mining, gravel hauling,
concrete, exploration, and military.

Variable Central Tire Inflation Systems

**CM Automotive Systems, Inc.** manufactures the ***Central Tire
Inflation System (CTIS**)*, which is designed for all terrain operations
more so than over-the-road operations. CM Automotive's targeted market
is military trucks and transports, fire and rescue vehicles, logging
operations, and dump trucks. The CTIS allows the driver to maintain
traction and mobility over wide variations of terrain by adjusting the
tire pressures. The tire adjustments can be made while the vehicle is in
motion. The system components are the manifold, controller, wheel valve,
and harness. The manifold adjusts pressure that goes to or out of the
system. The controller is the display located in the cab that allows the
driver to operate the system. The wheel valve attaches to the valve
stems and allows for the air to enter or escape the tires, and the
harness provides the electronic controls to the system. The cost of this
system on a tractor--trailer combination ranges from \$1,200 to \$2,500
depending on vehicle/axle configuration. *CM Automotive Systems, Inc.,
120 Commerce Way, Walnut, CA 91789, (909) 869-7912,
[[www.cmautomotive.com]{.underline}](http://www.cmautomotive.com/).*

**Tire Pressure Control International, LTD. (TPC International**)
manufactures and distributes the ***TIREBOSS Tire Pressure Control
System***. This system integrates with the existing air supply on the
vehicle. It is comprised of five component assemblies: a priority valve
that protects air brake system integrity, control air valves, air lines
to and from the control valves, and axle end rotary union hardware that
transmits air into and out of the rotating tires. In use, the driver
selects an appropriate setting on the operator control panel, which
sends a signal through the computer to either the inflate or deflate
control valves. Air from the vehicle brake wet tank is drawn into the
tire pressure control system to inflate tires through the inflate
valves, while air from the tires is exhausted through the deflate
valves. Priority safety switches make sure that air is available for
tire inflation only when the vehicle system air brake pressure is above
a safe level, typically

90 psi. The computer continuously monitors tire pressure and controls
the inflating, deflating, or maintaining of a pre-selected target tire
pressure. The system also monitors vehicle speed. If it detects the rig
is going too fast for the selected tire pressure and risking tire
damage, visual and audible alerts warn the operator to reduce speed or
choose another pressure setting. Should the driver fail to respond to
these alerts, the computer is programmed to automatically select a
pressure suitable for higher speeds. The operator control unit is easy
to read allowing the driver to monitor the status of the TPCS at a
glance. Four buttons control and program the system's functions, which
include four driving modes (i.e., highway loaded, highway unloaded,
off-highway loaded, and off-highway unloaded) as well as three secondary
function modes. This system is used primarily in on-off road
applications such as forestry and concrete operations where mobility in
sand or soft ground is required. The cost for this system starts at
about \$8,000 to equip the tandem drive axles on a tractor. *Tire
Pressure Control International Ltd., 15803 -- 121 A Avenue, Edmonton,
Alberta, Canada, T5V 1B1, (888) 338-3587,
[[www.tirepressurecontrol.com]{.underline}](http://www.tirepressurecontrol.com/).*

**Dana Corporation, Spicer Heavy Axle & Brake Division,** markets the
***Tire Pressure Control System***. Dana's Tire Pressure Control System
is designed specifically to allow the operator to adjust tire pressure
to match the conditions on and off the road while the vehicle is in
motion or is stationary. This system is the commercial version of the
Eaton Central Tire Inflation System used in military applications. This
system regulates tire pressures through a series of electro-pneumatic
controls that feed air to each wheel end through wheel valves. The
driver operates a dash-mounted graphic control panel, which commands the
system to adjust tire pressures, and tells the driver what functions the
system is currently performing. A pressure switch prevents the system
from consuming air unless the vehicle's brake system is fully charged.
This system has three distinct settings: a highway setting for high
speed travel on paved surfaces, an off-highway setting for operation on
secondary roads, and an emergency setting to help free vehicles that are
stuck in muddy terrain or to help drivers negotiate difficult grades.
Two modes accommodate both loaded and unloaded trucks. The cost for this
system on a tractor-trailer unit is about \$7,000 to \$13,000. Eaton
first introduced this to the truck market in 1990. No sales numbers are
available for this product. *Dana Corporation, Spicer Heavy Axle & Brake
Division, Advanced Chassis Control Unit, PO Box 4097, Kalamazoo, MI
49003-4097,(800) 826-4357,
[[www.roadranger.com]{.underline}](http://www.roadranger.com/).*

Constant Central Tire Inflation Systems

**Air Fender Systems, Inc.** has just developed its ***Rotary Air
Chamber*.** This system is designed for tractor (including steer tires)
and trailer tires and supplies air to them while traveling down the
road. The Rotary Air Chamber does this by taking air from the brake
system air tank and passing it into an internal air chamber that is
bolted on to the axles and rotates with the tires. The air then passes
through a small tunnel hole in the rotator shaft and comes out via a 'T'
connection that has two hoses connected to the valve stems of the dual
tires. The housing of the air chamber is held stationary by Air Fender's
fender panel. Tire pressure can be visually read by examining a small
pressure gauge on the hose lines that constantly measures the actual
tire pressure. Pressure is maintained at 100 psi, and air is exhausted
from the tires when pressures exceed 120 psi. This system costs about
\$80 an axle end. *Air Fender Systems, Inc., 322 Northpoint Parkway,
Suite J, Acworth, GA 30102, (800) 527-7729, John Becker, President,
[[www.airfenders.com]{.underline}](http://www.airfenders.com/).*

**AIRGO Systems Inc.** brought out a new central tire inflation system
in July 2003 called the ***AIRGO System***. The company founder, Tony
Ingram, was formerly with Pressure Systems International. The trailer
central tire inflation system has a light on the trailer nose that
indicates when the system is supplying pressure to the tires. The AIRGO
System offers constant tire monitoring and when necessary automatic
re-inflation. When a tire loses pressure due to a puncture or other
leakage, the system's sensor check valve automatically detects the loss.
It immediately draws air from the vehicle's reserve pneumatic system,
and directs air flow to each tire requiring air. This air pressure is
delivered via the trailer's hollow axle housing, through the hub
assembly and into the tires. The system uses an externally located
rotation design for venting outside of the hub, which eliminates
potential internal pressure leaks and debris that can cause damage to
internal hub components. Eight cubic feet per minute of air flow is
supplied to a leaking tire via a large transfer tube. The external
location of the rotating unit allows for fast installation and service
and no custom hubcaps are required. The rotary seal this system uses is
guaranteed to last 5 years. The suggested retail price is \$795 for a
tandem axle trailer. OEM and distributor pricing is available. *AIRGO
Systems, PO Box 727, Edmond, OK 73034, (405) 844-5825, Tony Ingram, CEO,
Julie Leidner Marketing, (617) 422-0045.*

**Arvin Meritor** distributes **Pressure System International's (PSI's)
*Tire Inflation System***. This system currently addresses only trailer
tires, but the company is working on developing a system for tractors as
well. The Tire Inflation System uses compressed air from the trailer to
inflate any tire that falls below pre-defined specifications. Air from
the existing trailer air supply is routed to a control box and then into
each axle. Acting as a conduit, the axles carry the air through a rotary
union assembly at the spindle end, which then distributes the air to
each tire as needed. Tire pressure is constantly monitored. When a tire
experiences a leak, an indicator light mounted onto the trailer comes on
to signal air delivery and that tires are being inflated. A one-way
check valve located in the hose connected to the valve stem protects
each tire against air pressure loss. If a tire is punctured during
operation and loses air pressure, the check valve prevents loss of
pressure in the other tires. A pressure protection valve located between
the shut-off valve and the reservoir allows air to flow to the tire
inflation system only when the brakes have sufficient pressure to
operate correctly. The cost for this system is approximately \$700.
*Arvin Meritor Commercial Vehicle Systems, Meritor Heavy Vehicle
Systems, LLC, 2135 West Maple Road, Troy, MI 48084, (800) 435-5560,
[[www.arvinmeritor.com]{.underline}](http://www.arvinmeritor.com/).
Pressure Systems International, 3023 Interstate Drive, San Antonio, TX
78219, (210) 222-1926, Frank Sonzala, Executive Vice President.*

**Dana Corporation, Spicer Heavy Axle & Brake Division,** produces the
***Tire Maintenance System for Trailers***. This system constantly
monitors tire pressure and provides air pressure automatically to
trailer tires that experience air loss. (It does not address tractor
tires.) This system detects and responds to low tire pressure by
directing air as needed and alerting the operator with a yellow light
located on the left front corner of the trailer. It also retains
evidence of low pressure tires in its memory for recall during vehicle
maintenance. The system uses a main power harness, an ECU, and a
pneumatic control valve to regulate air pressure to the tires. Air flows
through conduits inside the axle to wheel end seals. The price for this
system on an eight-wheeled trailer is \$900. This system was introduced
in 1999-2000. No unit sales numbers are available for this product.
*Dana Corporation, Spicer Heavy Axle & Brake Division, Advanced Chassis
Control Unit, PO Box 4097, Kalamazoo, MI 49003-4097,
[[www.roadranger.com]{.underline}](http://www.roadranger.com/).*

**Gio-Set Corporation** produces the ***Vigia Automatic Tire Pressure
System*** for tractors-trailer combinations and RVs**.** This system
continuously reports and automatically regulates the tire pressure. When
the pressure falls minimally in one or more tires, the Vigia system
reports the existence and location of the problem to the driver. At the
same time, the inflation process starts to maintain the appropriate
pressure in the tires. In case of a tire blowout, the equipment
automatically shuts down to protect the operation of the other
air-powered components on the vehicle such as the brakes, clutch,
suspension, etc. Air pressure is supplied from the auxiliary air
reservoir. A dedicated air filter absorbs the impurities in the air.
Once the air is filtered, it reaches the control panel and from there is
redistributed to the tires. A small control panel in the truck cab
controls all the functions in the system. The lights indicate the normal
function of the equipment, the loss of pressure in tires, the air
circuit where the loss is taking place, and the low air pressure of the
compressor. A separate control panel is placed on the front corner of
the trailer so that the driver can readily see it. This system costs
\$2,300 to \$3,200 depending on the axle setup for a tractor and trailer
combination. *Gio-Set Corporation, 37 Landing, Laguna Niguel, CA 92677,
(949) 412-9393, Ruben Giosa, Distributor.
[[www.gio-set.com]{.underline}](http://www.gio-set.com/).*

**Hendrickson International** began marketing its ***Hendrickson Tire
Inflation System* (HTIS)** for its INTRAAX and VANTRAAX trailer
suspension systems in 2002. This responsive tire maintenance system
maintains inflation to a specified level. The system checks tire
pressure every 10 minutes, detects low tire pressure, and alerts the
operator to the occurrence. It responds by directing air when a tire
dips below a predetermined pressure level. HTIS activates only when
needed--- constant air pressurization to the tires is ***not***
required---reducing air demand and prolonging system life. Air travels
from the supply tank through air lines inside the axle to the
wheel-ends. A rotary union allows air to flow from a non-rotating axle
spindle to the rotating hubcap fitting. Hoses connect from a hubcap tee
to the tires. A warning light alerts the operator to system status and
maintenance activity and the system records episodes of low tire
pressure for retrieval during servicing. Check valves help prevent tire
pressure loss back through the system. Manual fill and pressure checks
may be accomplished at the hose end. HTIS connects all tires to the
trailer air supply and may be combined with any of an extensive array of
wheel end configurations and spindles available for INTRAAX and VANTRAAX
suspensions only. A laptop computer can be used to download tire
inflation history from the system. The system was jointly developed by
Hendrickson and Spicer over a 2 ½ - to 3-year period, and was introduced
to the market in May 2002. Approximately 1,000 systems are currently in
use. Hendrickson sells this system only to trailer OEMs who price it
competitively with other similar systems on new trailers. As a result,
Hendrickson does not control the price.

Hendrickson introduced a new tire inflation system in 2003 called
***TIREMAXX*** that has less record-keeping features but is less costly.
This system is governed by an ECU that detects low tire pressure and
signals the operator. It responds by directing air from the trailer tank
to one or more tires when the pressure dips below the pre-set level. It
only pressurizes the air lines when needed, which protects seals and
wheel ends. A lamp is mounted onto the trailer to alert the driver to
the system status. An optional handheld programmer featuring a
32-character display accesses status information and, using convenient
system-check routines, reduces guesswork when troubleshooting. This
convenient maintenance tool reprograms target pressure to settings from
70 to 130 psi in 5-psi increments and helps prevent system tampering.
*Hendrickson International, Trailer Suspension Systems, 2070 Industrial
Place SE, Canton, OH 44707-2641, (866) 743-3247, Rick Bevington,
Marketing Manager, Tire Inflation Systems,
[www.hendrickson-intl.com]{.underline}.*

**Reineke Company Inc.** manufactures the ***PressureGuard Automatic
Tire Maintenance System*** (which it purchased from Innovative
Transportation Products Inc. (ITP) in 2003). The PressureGuard system
routes air from the trailer's supply tank through the axle to the hub
and then to the tires so they maintain pressure at preset levels. The
system is always under pressure so tire pressure is constantly
monitored. If there is a tire blowout or system leak, PressureGuard's
valve-stem-mounted check valve keeps air in the remaining tires. If a
sudden drop in pressure occurs, the system protection valve closes to
prevent air loss out of the reservoir so the rest of the trailer air
system including brakes remains unaffected. When a sudden loss of air
occurs, a trailer-only warning indicator alerts the driver. The cost of
the PressureGuard System for one trailer is about \$600. ITP worked on
developing this product for over a year before it introduced it to the
market in October 1999. Since then, it has sold around 20,000 units.
Reineke Company has been working with Tire-SafeGuard to offer a tire
monitoring system that will work in conjunction with the Pressure Guard
Automatic Tire Maintenance System, which will include a display in the
cab that advises the driver of individual tire air pressures

Reineke is also developing a drive axle tire inflation system. The
***Drive Axle TIS*** uses a rotary union that can be adapted to fit an
array of drive shaft designs. The system was designed for use without
complicated electronic components and to maintain correct tire pressure
at a preset level (inflate only). The cost for this system is expected
to be between \$2,000 and \$3,000.

***PressureGuard TIS*** for wide base tires is also under development.
This system uses a valve stem adapter that is inserted in a hole drilled
into the wheel and eliminates the need for hoses. The cost of this
system is expected to be from \$600 to \$700 per trailer. *Reineke
Company Inc., 1025 Faultless Drive, Ashland, OH 44805,(419) 281-5800,
Matt Reineke, President,
[[www.pressureguard.com]{.underline}](http://www.pressureguard.com/).*

Continuous Tire Pressure Pumps

The **Cycloid Company** produced the ***Cycloid Model 2000 Continuous
Tire Pressure Maintenance System***. This system was different from the
other tire inflation systems as it did not use the air system on the
vehicle to supply air to the tires, but rather generated its own
compressed air with a small pump mounted onto the end of each axle. The
rolling motion of the wheel (centrifugal force) continuously powered the
Cycloid self-contained pump compressor. It attached to the hub of a dual
wheel assembly and hoses connected the pump to the tire valve stems.
Inner and outer tire pressures could easily be checked from a
centralized hub-mounted valve stem. An option was available that
provided visible pressure gauges to indicate the exact pressure in the
tire assemblies. The pump was set at the factory with the maximum
pressure to which the tire would be inflated so it would not
over-inflate or deflate the tires. The pump constantly monitored tire
pressure. When a tire experienced an air leak, the pump supplied air
independently to that tire. It did not equalize pressure between the
dual tires. Due to overall width limitations on commercial vehicles, the
pump could only be installed on dual wheel combinations and could not be
placed on steer axle ends. The pump weighed 2 lbs. and pumped 6 psi an
hour to tires that experienced air loss. The cost of a Cycloid Model
2000 Pump ranged from \$200 to \$250 an axle end depending upon the
accessories chosen.

In 2001, Cycloid signed an exclusive distribution contract with Euclid
Industries for sale of their truck tire pump. However, on the same day,
Euclid was purchased by Arvin Meritor, which already had an exclusive
agreement with Pressure Systems International for distribution of its
Tire Inflation System. As a result, Cycloid decided to exit the
commercial truck market and concentrate on the automotive market with
its pump through its ties with Arvin Meritor. At this moment, the
company does not sell pumps for commercial trucks. Cycloid began
developing its Continuous Tire Pressure Maintenance System in 1992 and
introduced it to the market in 1997. It has sold 7,000 pumps in the
trucking industry. *Cycloid Company, 301 Commerce Park Drive, Cranberry
Township, PA 16066, (724) 742-1780, Mervyn Carse, President and CEO.*

Other Technologies

With the advent of the Firestone recall in 2000, new and innovative
technologies are being explored to address the problem of tire failures.
Some of these technologies do not fit the general category of tire
pressure monitors, but do address detection of tire failures. One such
technology is described below.

**Radian Inc.** has developed the ***Thermal Imaging Inspection Station
(TIIS)***. This system uses thermal imagery to detect tire faults that
result in tire failures due to heat buildup inside a tire. In tires,
most tire failures begin with separation in the plies. Air eventually
seeps into these areas of separation and heats up and expands when the
vehicle is moving. The air trapped in the separations becomes hotter
than the air in the tire, which causes the separations to expand until a
chunk of rubber breaks off and causes a blowout. The pattern of heat
that builds up can be viewed with a thermal imager (camera) that takes
temperature sensitive snap shots of tires. The TIIS detects these
separations that show up as red in the photographs and is programmed to
recognize the thermal signatures associated with separations to give
advanced warning of an impending failure. The TIIS can be used in any
location where vehicles have been in operation at highway speeds. Weigh
stations on interstate highways and the entrance into maintenance yards
are good sites for inspecting tires. Vehicles can be moving at speeds up
to 15 mph while going through the TIIS inspection. The TIIS can also be
mounted in a vehicle and a handheld unit may be available in the future
too. In addition, this system can be used to detect overheating brakes
and bearings. The cost of the TIIS is currently about \$90,000 to
\$100,000. Radian, however, is working on making a smaller, handheld
version that will have a target price of around \$20,000. *Radian, Inc.,
5845 Richmond Highway, Alexandria, VA 22303, (703) 329-9300,
[www.radianinc.com](http://www.radianinc.com/).*

![](media/image1.png){width="2.6638888888888888in"
height="0.8638888888888889in"}

[^1]: Federal Motor Carrier Safety Administration, *Commercial Vehicle
    Tire Condition Sensors*, United States Department of Transportation,
    Washington, DC, 2003.

[^2]: Federal Motor Carrier Safety Administration, *Commercial Vehicle
    Tire Condition Sensors*, Report \# FMCSA-PSV-04-002, United States
    Department of Transportation, Washington, DC, 2003.

[^3]: Link Manufacturing, Ltd., 223 15th Street, N.E., Sioux Center, IA
    51250-2120, (800) 222-6283, Pat Coghlan, National Sales Director,
    [[www.linkmfg.com]{.underline}](http://www.linkmfg.com/).

[^4]: V-Tech International, Inc., 227 Barbie Drive, West Bend, WI 53090,
    (262) 306-1708, Gottfried Hoffmann, President,
    [[www.vtechint.com]{.underline}](http://www.vtechint.com/)

[^5]: Advantage Pressure Pro LLC, Inc., 205 Wall Street, Harrisonville,
    MO 64701, (800) 959-3505, Phil Zaroor, President,
    [[www.advantagepressurepro.com]{.underline}](http://www.advantagepressurepro.com/)

[^6]: WABCO GmbH, Vehicle Control Systems, Am Lindener Hafen 21,
    D-30453, Hanover, Postfach 91 21 62, Germany,

    49-511-922-2144,
    [*[www.ivtm.com]{.underline}*](http://www.ivtm.com/).

[^7]: HCI Corporation, 11245 E. 183rd Street, Cerritos, CA 90703, (562)
    926-7123 x 212, Tim Glassford, Sales Manager,
    [[www.tiresafeguard.com]{.underline}](http://www.tiresafeguard.com/).

[^8]: SmarTire Systems, Inc., Suite 150 -- 13151 Vanier Place, Richmond,
    BC, Canada V6V 2J1, (604) 276-9884 x 308, John Bolegoh, Product
    Manager,
    [*[www.smartire.com]{.underline}*](http://www.smartire.com/).

[^9]: Michelin North America Inc., PO Box 19011, Greenville, SC 29602,
    (864) 458-5476, Randy Clark, Vice President of Marketing, Truck Tire
    Unit,
    [*[www.michelintruck.com]{.underline}*](http://www.michelintruck.com/).

[^10]: Arvin Meritor Commercial Vehicle Systems, Meritor Heavy Vehicle
    Systems, LLC, 2135 West Maple Road, Troy, MI 48084, (800) 435-5560,
    [*[www.arvinmeritor.com]{.underline}*](http://www.arvinmeritor.com/).
    Pressure Systems International, 3023 Interstate Drive, San Antonio,
    TX 78219, (210) 222-1926, Frank Sonzala, Executive Vice President.

[^11]: Gio-Set Corporation, 37 Landing, Laguna Niguel, CA 92677, (949)
    412-9393, Ruben Giosa, Distributor.

    [[*www.gio-set.com*](http://www.gio-set.com/).]{.underline}

[^12]: Dynamic Sealing Technologies Incorporated, 13941 Lincoln Street
    NE, Minneapolis, MN 55304, (763) 786-3758,
    [www.dynamicsealing.com]{.underline}*.*

[^13]: Not associated with Link Manufacturing, which produces the "Cat's
    Eye" equalizer tested in this study.

[^14]: Data can be obtained from the Federal Motor Carrier Safety
    Administration (FMCSA), Office of Bus and Truck Standards and
    Operations (MC-PSV), 400 7th Street, SW, Washington, DC 20590-0001.

[^15]: A second warning was also available from this system, but the
    threshold where this warning occurred was not tested due to an
    initial failure to record the warning with the data acquisition
    system, which was later corrected.

[^16]: This value is configurable by the vehicle operator.

[^17]: McNamee, Thomas, e-mail to the authors, December 16, 2005.

[^18]: It should also be noted that for the leak rates of 5.0 and 10.0
    psi/min, the initial sharp decrease in pressure is not a result of
    rapid loss of tire pressure, but rather of the pressure transducer
    being plumbed into the same air line as the leak orifice---the high
    rate of flow through the line appears to the pressure transducer as
    a lower pressure.