Tire Rolling Resistance, Its Impact on 

Fuel Economy, and Measurement 

Standards

Presented to the California Energy Commission

by 

Tim J. LaClair, Ph.D.
CEC Workshop on Fuel Efficient Tires

 Definition: "Rolling resistance is the energy consumed per unit 

distance and is equivalent to the scalar sum of all contact forces 

tangent to the test surface and parallel to the wheel plane of the 

tire" (SAE J2452)

 Units are [J/m] or simply [N], but conceptually, rolling resistance 

Rolling Resistance Basics

 Units are [J/m] or simply [N], but conceptually, rolling resistance 

is better comprehended as a loss per distance than a force

 Rolling resistance is primarily due to viscoelastic heat dissipation 

in the rubber

 Aerodynamic drag, friction in the contact patch, and friction with 

the rim also contribute to the total rolling resistance, FR
CEC Workshop on Fuel Efficient Tires

 Loss contributions:

Rolling Resistance Basics

Aerodynamic

Drag

Tire/ground

and tire/rim

friction (<5%) 

Hysteretic losses

80 to 95 %

0 to 15%
CEC Workshop on Fuel Efficient Tires

RR Impact on Fuel Consumption

 Fuel energy is dissipated by many vehicle losses, including 

rolling resistance:

(National Research Council, "Automotive Fuel Economy: How Far Should We Go?", 1992)
CEC Workshop on Fuel Efficient Tires

RR Impact on Fuel Consumption

% Reduction in Rolling Resistance

% Reduction in Fuel Consumption

Return Factor 

 To better quantify and understand the contribution of rolling 

resistance to fuel economy, Schuring (1988) proposed the 

concept of the Return Factor (also referred to as energy ratio):

% Reduction in Rolling Resistance

Return Factor 

 For passenger cars and light trucks, RF is typically between 1:10 

and 2:10. This indicates that a 10% improvement in RR gives 

only a 1-2% improvement in fuel economy.

 For heavy trucks, RF can be higher, with a typical range between 

1:10 and 3:10, hence the fuel savings potential for trucks may be 

higher than for passenger vehicles
CEC Workshop on Fuel Efficient Tires

RR Impact on Fuel Consumption
CEC Workshop on Fuel Efficient Tires

 In response to CAFE and a sense of environmental stewardship, 

the tire and rubber industries have responded to dramatically 

reduce rolling resistance since 1980:

RR Impact on Fuel Consumption

150

175

50

75

100

125

150

1975 1980 1985 1990 1995 2000

Year

Rolling Resistance Index

(Lowest Michelin FR high-volume construction at 80% of the T&RA 1.8 bar load, 2.6 bar, 80 kph)
CEC Workshop on Fuel Efficient Tires

 In North America, the current rolling resistance standard is SAE 

J2452, which superseded SAE J1269 in 1999

 In 1995, EPA mandated a true load matching procedure which 

would enable dynamometer simulation of road forces across a 

range of speeds for emissions certification and fuel economy 

Rolling Resistance Measurements

range of speeds for emissions certification and fuel economy 

testing

 Therefore, for coastdown and performance modeling, auto 

manufacturers require component-level data, including FR, as a 

function of speed 

 The new method measures the dependence of FR on speed, in 

addition to load and pressure, which is its primary benefit
CEC Workshop on Fuel Efficient Tires

Rolling Resistance Measurements

 Using the rolling resistance model and coefficients , , a, b, and 

c deduced from the J2452 coastdown data:

  

 



f

t

t

P L a bV cV t

MERF 0

d

  2

 For North America, the natural choice of velocity cycles are the 

EPA Urban and Highway cycles used for emissions certification 

and fuel economy measurement





f

t

t

t

MERF

0

d
CEC Workshop on Fuel Efficient Tires

Rolling Resistance Measurements

 Using MERF the RR can be more accurately applied to fuel 

economy predictions for a particular drive cycle

 However, there is no direct correlation between RR values 

measured with SAE J1269 and SAE J2452

 Largely for this reason, SAE J2452 has been adopted slowly: 

transition to the new standard is still not complete

 For replacement and OE markets there is a bit of a mixture of 

data between the two standards

 Furthermore, for the replacement tire market RR is not a 

significant performance target and in many cases data has not 

been measured
CEC Workshop on Fuel Efficient Tires

Rolling Resistance and Other Performances

 Tire design requires balancing performances since changes in 

design may change different performances in opposing directions

 For the OE market, a tire is designed for a single vehicle and the 

characteristics of the tire are optimized for that vehicle only

 On the other hand, for the replacement market, tires need to be 

designed to provide a balanced set of performances for a wide 

variety of vehicle types with different handling characteristics, 

etc.

 For this reason, rolling resistance is frequently higher for 

replacement market tires than a tire designed for use with a 

particular vehicle
CEC Workshop on Fuel Efficient Tires

Rolling Resistance and Other Performances

 Rolling resistance is affected by many factors, both in tire design 

and operating conditions:

– Tire Mass

– Rubber Formulations

– Inflation Pressure

– Speed

– Ambient/Tire Temperature

– Applied Drive Torque

– Surface Roughness

– Steer angle and camber/toe of vehicle
CEC Workshop on Fuel Efficient Tires

Possible Approaches for Obtaining RR Data

 Obtaining RR data for which a direct comparison can be made 

will require a significant effort and cost

 Two basic approaches may be envisioned:

– RR testing could be performed, for several tires having a 

range of RR values, at different sites in a “Round Robin”. A 

correlation would be established between sites which would 

then be applied to allow direct comparison of measured data 

from the different sites

– Alternatively, an independent laboratory could be contracted 

to perform all necessary RR testing

 The first approach may be more cost effective since any existing 

data could be used, but the second approach may provide more 

reliable results