Document ID: chunk:federal_register_of_legislation:F2021C01192:body:0:p49
Version: federal_register_of_legislation:F2021C01192
Segment Type: other
Provision Reference: 
Character Range: 129841–132433

the axle to reach maximum performance. The anti-lock system shall be disconnected, or inoperative, between 40 km/h and 20 km/h.
1.1.3.  A number of tests at increments of line pressure shall be carried out to determine the maximum braking rate of the vehicle (zmax). During each test, a constant input force shall be maintained and the braking rate will be determined by reference to the time taken (t) for the speed to reduce from 40 km/h to 20 km/h using the formula:

  zmax is the maximum value of z; t is in seconds.
1.1.3.1.  Wheel lock may occur below 20 km/h.
1.1.3.2.  Starting from the minimum measured value of t, called tmin , then select three values of t comprised within tmin and 1.05 tmin and calculate their arithmetical mean value tm ,
then calculate:
  If it is demonstrated that for practical reasons the three values defined above cannot be obtained, then the minimum time tmin may be utilized. However, the requirements of paragraph 1.3. shall still apply.
1.1.4.  The braking forces shall be calculated from the measured braking rate and the rolling resistance of the unbraked axle which is equal to 0.015 and 0.010 of the static axle load for a driven axle and a non-driven axle, respectively.
1.1.5.  The dynamic load on the axle shall be that given by the formulae in Annex 5 to this Regulation.
1.1.6.  The value of k shall be rounded to three decimal places.
1.1.7.  Then, the test will be repeated for the other axle(s) as defined in paragraphs 1.1.1. to 1.1.6. above.
1.1.8.  For example, in the case of a two-axle rear-wheel drive vehicle, with the front axle (1) being braked, the coefficient of adhesion (k) is given by:

  The other symbols (P, h, E) are defined in Annex 5 to this Regulation.
1.1.9.  One coefficient will be determined for the front axle kf and one for the rear axle kr.
1.2.  Determination of the adhesion utilized ()
1.2.1.  The adhesion utilized () is defined as the quotient of the maximum braking rate with the anti-lock system operative (zAL) and the coefficient of adhesion ( kM ) i.e.,

1.2.2.  From an initial vehicle speed of 55 km/h, the maximum braking rate (zAL) shall be measured with full cycling of the anti-lock braking system and based on the average value of three tests, as in paragraph 1.1.3. of this appendix, using the time taken for the speed to reduce from 45 km/h to 15 km/h, according to the following formula:

1.2.3.  The coefficient of adhesion kM shall be determined by weighting with the dynamic axle loads.

 where:

1.2.4.  The value of  shall be rounded to two decimal places.
1.2.5.  In the case