ISO/FDIS 28580

Passenger car, truck and bus tyre rolling resistance measurement methods — Single point test and correlation of measurement results

This document specifies methods for measuring rolling resistance, under controlled laboratory conditions, for new pneumatic tyres designed primarily for use on passenger cars, trucks and buses. This document is not applicable to tyres intended for temporary use only. It includes a method for correlating measurement results to allow inter-laboratory comparisons. It is designed to facilitate international cooperation and, possibly, regulation building. Measurement of tyres using this method enables comparisons to be made between the rolling resistance of new test tyres when they are free-rolling straight ahead, in a position perpendicular to the drum outer surface, and in steady-state conditions.

Méthodes de mesure de la résistance au roulement des pneumatiques pour voitures particulières, camions et autobus — Essai à condition de mesure unique et corrélation des résultats de mesure

Le présent document prescrit des méthodes de mesure de la résistance au roulement, dans des conditions de laboratoire maîtrisées, pour des pneumatiques neufs conçus essentiellement pour être utilisés sur des voitures particulières, des camions et des autobus. Le présent document ne s'applique pas aux pneumatiques destinés à un usage temporaire. Il comporte une méthode de corrélation des résultats de mesure destinée à permettre les comparaisons inter laboratoires. Il est conçu pour faciliter la coopération internationale et, éventuellement l'élaboration de réglementations. Le mesurage de pneumatiques selon cette méthode permet d'établir des comparaisons entre la résistance au roulement de pneumatiques d'essai neufs lorsqu'ils roulent librement en ligne droite, dans une position perpendiculaire à la surface extérieure du tambour et dans des conditions stabilisées.

General Information

• Status: Not Published
• ICS: 83.160.01 - Tyres in general
• ICS: 83.160.10 - Road vehicle tyres
• Technical Committee: ISO/TC 31 - Tyres, rims and valves
• Drafting Committee: ISO/TC 31/WG 6 - Rolling resistance (highway tyres)
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 24-Jun-2026
• Completion Date: 24-Jun-2026

Relations

• Revises: ISO 28580:2018 - Passenger car, truck and bus tyre rolling resistance measurement method — Single point test and correlation of measurement results
• Effective Date: 31-Aug-2024
• Revises: ISO 18164:2005 - Passenger car, truck, bus and motorcycle tyres — Methods of measuring rolling resistance
• Effective Date: 31-Aug-2024

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/TC 31
Passenger car, truck and bus tyre
Secretariat: ANSI
rolling resistance measurement
Voting begins on:
methods — Single point test and
2026-06-24
correlation of measurement results
Voting terminates on:
2026-08-19
Méthodes de mesure de la résistance au roulement des
pneumatiques pour voitures particulières, camions et autobus —
Essai à condition de mesure unique et corrélation des résultats de
mesure
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 31
Passenger car, truck and bus tyre
Secretariat: ANSI
rolling resistance measurement
Voting begins on:
methods — Single point test and
correlation of measurement results
Voting terminates on:
Méthodes de mesure de la résistance au roulement des
pneumatiques pour voitures particulières, camions et autobus —
Essai à condition de mesure unique et corrélation des résultats de
mesure
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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Published in Switzerland Reference number
ii
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test methods . 4
5 Test equipment . 4
5.1 General .4
5.2 Drum specifications .4
5.2.1 Diameter .4
5.2.2 Surface .4
5.2.3 Width .5
5.3 Measuring rim .5
5.4 Load, alignment, control and instrumentation accuracies .5
5.5 Thermal environment .5
5.5.1 Reference conditions .5
5.5.2 Alternative conditions .5
6 Test conditions . 5
6.1 General .5
6.2 Test speeds .5
6.3 Test load .6
6.4 Test inflation pressure .6
6.5 Duration and speed .6
6.6 Optional test conditions .6
7 Test procedure . 6
7.1 General .6
7.2 Thermal conditioning .6
7.3 Pressure adjustment .7
7.4 Warm-up .7
7.5 Measurement and recording .7
7.6 Measurement of parasitic losses .8
7.6.1 General .8
7.6.2 Skim test reading .8
7.6.3 Deceleration method.8
7.7 Allowance for machines exceeding σ criterion .9
m
8 Data interpretation . 9
8.1 Determination of parasitic losses .9
8.1.1 General .9
8.1.2 Force method at tyre spindle .9
8.1.3 Torque method at drum axis .10
8.1.4 Power method at drum axis .10
8.1.5 Deceleration method.10
8.2 Rolling resistance calculation .10
8.2.1 General .10
8.2.2 Force method at tyre spindle .10
8.2.3 Torque method at drum axis .11
8.2.4 Power method at drum axis .11
8.2.5 Deceleration method.11
9 Data analysis .12
9.1 Rolling resistance coefficient . 12
9.2 Temperature correction . 12
9.3 Drum diameter correction . 12
9.4 Measurement result . 13

iii
10 Measurement machines alignment and monitoring requirements .13
10.1 General . 13
10.2 Conditions for reference machine .14
10.3 Conditions for candidate machine .14
10.4 Alignment tyre requirements .14
10.5 Alignment procedure . 15
Annex A (normative) Test equipment tolerances . 17
Annex B (informative) Measurement methods of moment of inertia for drum and tyre assembly
— Deceleration method . 19
Annex C (informative) Test rim runout .23
Annex D (informative) Publications of tyre standards .24
Annex E (informative) Example for larger truck bus warm-up duration .25
Annex F (informative) Example for machine drift evaluation .26
Annex G (informative) Optional test conditions .29
Bibliography .31

iv
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
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The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
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related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by ISO/TC 31, Tyres, rims and valves.
This third edition cancels and replaces the second edition (ISO 28580:2018), which has been technically
revised.
The main change is as follows:
— addition of Annex G with optional test conditions regarding sensitivity to test speed, tyre load and
inflation pressure.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
FINAL DRAFT International Standard ISO/FDIS 28580:2026(en)
Passenger car, truck and bus tyre rolling resistance
measurement methods — Single point test and correlation of
measurement results
1 Scope
This document specifies methods for measuring rolling resistance, under controlled laboratory conditions,
for new pneumatic tyres designed primarily for use on passenger cars, trucks and buses.
This document is not applicable to tyres intended for temporary use only. This document also specifies a
method for correlating measurement results to allow inter-laboratory comparisons.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 4000-1:2024, Passenger car tyres and rims — Part 1: Tyres (metric series)
ISO 4209-1, Truck and bus tyres and rims (metric series) — Part 1: Tyres
ISO 4223-1, Definitions of some terms used in the tyre industry — Part 1: Pneumatic tyres
ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4223-1 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
rolling resistance
F
r
loss of energy (or energy consumed) per unit of distance travelled
Note 1 to entry: The SI unit conventionally used for the rolling resistance is the newton metre per metre (N m/m). This
is equivalent to a drag force in newtons (N).
3.2
rolling resistance coefficient
C
r
ratio of the rolling resistance to the load on the tyre
Note 1 to entry: Rolling resistance is measured in newtons (N).
Note 2 to entry: Load on the tyre is measured in kilonewtons (kN).

Note 3 to entry: Although this quantity is dimensionless, it is conventionally expressed in N/kN.
3.3
capped inflation
process of inflating the tyre to the required cold pressure and allowing the inflation pressure to build up as
the tyre is warmed up while running
3.4
parasitic loss
loss of energy (or energy consumed) per unit distance excluding internal tyre losses, and attributable to
aerodynamic loss of the different rotating elements of the test equipment, bearing friction and other sources
of systematic loss which can be inherent in the measurement
Note 1 to entry: This document describes which of them are to be excluded from the result of the measurement.
3.5
skim test reading
type of parasitic loss measurement, in which the tyre is kept rolling, without slippage, while reducing the
tyre load to a level at which energy loss within the tyre itself is virtually zero
3.6
moment of inertia
ratio of the torque applied to a rotating body, such as a tyre assembly or machine drum, to the rotational
acceleration of this body
Note 1 to entry: See Annex B.
3.7
new test tyre
tyre which has not been previously used in a rolling deflected test which elevates the tyre’s temperature to
higher than that generated in rolling resistance tests or has not been exposed to a temperature higher than
40 °C
Note 1 to entry: Repetition of allowed test procedures is permitted.
Note 2 to entry: See examples in this document and in ISO 18164, SAE J1269, and SAE J2452.
3.8
correlation of measurement results
computations on a set of rolling resistance measurements to be carried out on a regular time basis by
separate laboratories in order to allow direct comparisons between their rolling resistance results
Note 1 to entry: The results of these measurements are used to compute "alignment" corrective coefficients and
permit calculation of aligned rolling resistance measurement, C (see Clause 10).
r aligned
3.9
reference machine
any machine considered as a reference for an alignment
Note 1 to entry: Every tyre testing spindle in one specific measurement method is considered a machine for the
purposes of this document. For example, two spindles acting on the same drum shall not be considered as one machine.
One spindle able to measure tyre rolling resistance through different methods shall not be considered as one machine.
3.9.1
physical reference machine
machine (and its corresponding laboratory quality systems) used to set alignment values
3.9.2
virtual reference machine
several machines (and their corresponding laboratory quality systems) used to set alignment values

3.10
candidate machine
machine intended to measure new test tyres, with alignment to a reference machine
3.11
alignment tyres
set of tyres measured by both the candidate and reference machines to perform machine alignment
3.12
laboratory control tyre
tyre used by an individual laboratory to control machine behaviour, e.g. machine drift, as a function of time
3.13
measurement repeatability
σ
m
dispersion of the results obtained on one machine for different measurements performed on the same
tyre(s) over a short period of time under the same testing conditions
Note 1 to entry: Measurement repeatability is estimated by measuring n + 1 times the whole process described in
Clause 7 (n ≥ 3) for p alignment tyres, assuming that the variances of the alignment tyres are homogeneous:
n1 n1
 
1 1 1
p 2
 
 with   C  C
 
mmi1 ,i m,iirr,,ji j
 
p ()n1 n
j2 j2
 
where
p is the number of alignment tyres;
i is the counter from 1 to p for the alignment tyres;
j is the counter from 2 to n + 1 for the n last repetitions of each measurement of a given alignment
tyre;
n + 1 is the number of repetitions of tyre measurements (n + 1=4 for reference laboratories
and n + 1 ≥ 4 for candidate laboratories). The last n measurement results are used for the
computation.
3.14
machine drift
change in the measured value over time which can be attributed to systematic (or progressive) sources of
variation
3.15
passenger car tyre
tyre of a group intended for application on 4-wheeled vehicles designed primarily for carrying fewer than
10 persons
Note 1 to entry: See Annex D for a list of standards which identify this tyre type.
3.16
truck and bus tyre
tyre of a group intended for application on vehicles designed primarily for the transportation of property or
for carrying more than 10 persons
Note 1 to entry: Such tyres are normally primarily designed for use on light trucks, trucks, buses and their trailers and
include those tyres marked with “LT”, “C”, “ST”, “CP”.
Note 2 to entry: See Annex D for a list of standards which identify this tyre type.
3.16.1
smaller truck and bus tyre
truck and bus tyre with a load index of 121 and smaller or, where the load index is not marked, a maximum
load of 1 450 kg and lower
3.16.2
larger truck and bus tyre
truck and bus tyre with a load index greater than 121 or, where the load index is not marked, a maximum
load of more than 1 450 kg
4 Test methods
This document is designed to facilitate international cooperation and, possibly, regulation building.
Measurement of tyres using the methods of this document enables comparisons to be made between the
rolling resistance of new test tyres when they are free-rolling straight ahead, in a position perpendicular to
the drum outer surface, and in steady-state conditions.
During the measurement of rolling resistance using the methods of this document, the value of the rolling
circumference of the tyre can be derived using the drum method provided in either ISO 9112 or ISO 17269.
The following are alternative measurement methods. The choice of an individual method is left to the tester.
For each method, the test measurements shall be converted to a force acting at the tyre-drum interface. The
measured parameters are:
a) Force method: the reaction force measured or converted at the tyre spindle (see NOTE 1).
b) Torque method: the torque input measured at the test drum (see NOTE 2).
c) Deceleration method: the measurement of deceleration of the test drum and tyre assembly (see NOTE
2).
d) Power method: the measurement of the power input to the test drum (see NOTE 2).
NOTE 1 This measured value also includes the bearing and aerodynamic losses of the wheel and tyre which are also
to be considered for further data interpretation.
NOTE 2 This measured value also includes the bearing and aerodynamic losses of the wheel, the tyre, and the drum
losses which are also to be considered for further data interpretation.
5 Test equipment
5.1 General
In measuring tyre rolling resistance, small forces shall be measured in the presence of much larger forces. It
is, therefore, equipment and instrumentation of appropriate accuracy shall be used.
5.2 Drum specifications
5.2.1 Diameter
The test dynamometer shall have a cylindrical flywheel (drum) with a diameter of at least 1,7 m.
The F and C values shall be expressed relative to a drum diameter of 2,0 m. If a drum diameter other than
r r
2,0 m is used, a correlation adjustment shall be made following the method specified in 9.3.
5.2.2 Surface
The surface of the drum shall be smooth steel. Optionally, a textured surface may also be used in order to
improve skim test reading accuracy. It shall be kept clean.
The F and C values shall be expressed relative to the “smooth” drum surface. If textured drum surface is
r r
used, see Clause A.6.
5.2.3 Width
The width of the drum test surface shall exceed the width of the test tyre contact patch.
5.3 Measuring rim
The tyre shall be mounted on a steel or light alloy measuring rim, with the width as defined in ISO 4000-1
for passenger car tyre rims and as defined in ISO 4209-1 for truck and bus tyre rims. If a size is not included
in ISO 4000-1 or ISO 4209-1, refer to the relevant calculation section. Mounting tyres on other rim widths
shall be done with the agreement of the requestor and the tester and such deviation shall be noted on the
test report. Rim runout guidelines are listed in Annex C.
5.4 Load, alignment, control and instrumentation accuracies
Measurement of these parameters shall be sufficiently accurate and precise to provide the required test
data. The specific and respective values are shown in Annex A.
5.5 Thermal environment
5.5.1 Reference conditions
The reference ambient temperature, as measured at a distance from the tyre sidewall of not less than 0,15 m
and not more than 1 m, shall be 25 °C.
5.5.2 Alternative conditions
If the test ambient temperature is different from the reference ambient temperature, the rolling resistance
measurement shall be corrected to the reference ambient temperature in accordance with 9.2.
6 Test conditions
6.1 General
The test consists of a measurement of rolling resistance in which the tyre is inflated to the required cold
pressure and the inflation pressure allowed to build up (i.e. “capped inflation”).
Any measurement other than what is prescribed within this document shall be done under the requestor’s
responsibility and should be noted on the test report (e.g. retread tyres, buffed tyres, different rim width,
pressures, loads, etc.). Studded tyres are not allowed due to potential drum damage.
6.2 Test speeds
The rolling resistance coefficient value shall be obtained at a drum speed as shown in Table 1.
Table 1 — Test speeds
Speeds in km/h
Tyre type Passenger Smaller truck and Larger truck and bus
car bus
a
Speed symbol All All J (100 km/h) and lower K (110 km/h)
and higher
Speed 80 80 60 80
a
If the tyre is not marked with a speed symbol, consult the manufacturer databook for the maximum rated
speed and select a test speed of 60 km/h for maximum rated speed of 100 km/h or lower; otherwise, test speed
is 80 km/h.
6.3 Test load
The standard test load shall be computed from the values shown in Table 2 and shall be kept within the
tolerance specified in Annex A.
6.4 Test inflation pressure
The inflation pressure shall be in accordance with what is shown in Table 2 and shall be capped with the
accuracy specified in A.4.
Table 2 — Test loads and inflation pressures
a b
Tyre type Passenger car Truck and bus
Standard load or Reinforced or extra load
light load
c
Load — % of maximum load 80 80 85
capacity (% of single load)
d
Inflation pressure 210 250 Corresponding to maximum sin-
e
gle tyre load carrying capacity
kPa
a
For those passenger car tyres belonging to categories which are not shown in ISO 4000-1:2024, Annex B, the inflation
pressure shall be the inflation pressure recommended by the tyre manufacturer, corresponding to the maximum tyre load
capacity, reduced by 30 kPa.
b
If there are multiple values given, the highest load and corresponding pressure should be selected, disregarding any
additional service description, which, if present, is located in a circle close to the primary service description.
c
85 % of maximum load capacity for single application specified in applicable tyre standards manuals.
d
The inflation pressure shall be capped with the accuracy specified in A.4.
e
Inflation pressure as specified in applicable tyre standards manuals corresponding to maximum single tyre load carrying
capacity.
6.5 Duration and speed
When the deceleration method is selected, the following requirements apply:
a) For duration Δt, the time increments shall not exceed 0,5 s.
b) Any variation of the test drum speed shall not exceed 1 km/h within one-time increment.
6.6 Optional test conditions
If the sensitivities of the rolling resistance of a tyre to test speed, tyre load or inflation pressure are desired,
the additional information in Annex G should be consulted.
7 Test procedure
7.1 General
The test procedure steps described below are to be followed in the sequence given.
7.2 Thermal conditioning
Place the inflated tyre in the thermal environment of the test location for a minimum of 3 h for passenger car
tyres and a minimum of 6 h for truck and bus tyres.

7.3 Pressure adjustment
After thermal conditioning, the inflation pressure shall be adjusted to the test pressure and verified 10 min
after the adjustment is made.
7.4 Warm-up
Warm-up duration is given in Table 3.
Table 3 — Warm-up duration
a
Tyre type Passenger Smaller truck Larger truck and bus
car and bus
Nominal rim All All <22,5 ≥22,5
diameter code
Warm-up dura- 30 min 50 min 150 min 180 min
tion
a
For the torque and force methods, larger truck and bus warm-up duration can be decreased
from the specified values if the following requirements are met:
a) Real time machine monitoring is available for input torque or spindle force with data averages
every minute.
b) It can be demonstrated that a tyre has reached a stabilized steady-state value of rolling
resistance when the absolute difference between data samples over a 10 min period is ≤0,1 N.
An example is provided in Annex E. The warm-up duration shall be indicated on the test report if
different from that shown in the table.
7.5 Measurement and recording
The following shall be measured and recorded (see Figure 1):
a) Test speed, U .
n
b) Load on the tyre normal to the drum surface, L
m
c) Test inflation pressure: initial, as defined in 6.4.
d) Rolling resistance coefficient measured, C , and its corrected value, C , at 25 °C and for a drum diameter
r rc
of 2 m.
e) Distance from the tyre axis to the drum outer surface under steady state conditions, in metres, r .
L
f) Ambient temperature, t .
amb
g) Test drum radius, R.
h) Test method chosen.
i) Test rim (size and material). If not the prescribed measuring rim, the deviation shall be highlighted.
j) Tyre identification such as: size, manufacturer, type, and, if it exists, SS, LI, Load Range, DOT Tire
Identification number and/or serial number.
All the mechanical quantities (forces, torques) shall be orientated according to ISO 8855. The directional
tyres shall be run in their specified rotation sense.

Key
1 tyre
2 drum
Figure 1 — Measurement orientation
7.6 Measurement of parasitic losses
7.6.1 General
The parasitic losses shall be determined by one of the procedures given in 7.6.2 or 7.6.3.
7.6.2 Skim test reading
a) Reduce the load to maintain the tyre at the test speed without slippage. The load values should be as
follows:
1) Passenger car tyres: recommended value of 100 N; not to exceed 200 N.
2) Smaller truck and bus tyres (LI ≤ 121): recommended value of 150 N; not to exceed 200 N for
machines designed for passenger car tyre measurement or 500 N for machine designed for truck
and bus tyres.
3) Larger truck and bus tyres (LI > 121): recommended value of 400 N; not to exceed 500 N.
4) Skim values shall be the same for both standard testing and alignment (Clause 10).
b) Record the spindle force, F , input torque, T , or the power, whichever applies.
t t
c) Record the load on the tyre normal to the drum surface, L .
m
NOTE 1 Except for the force method, the measured value includes the bearing and aerodynamic losses of the wheel,
the tyre, and the drum losses. For the force method, the measured value includes the bearing and aerodynamic losses
of the wheel and the tyre.
NOTE 2 It is known that the spindle and drum bearings friction depends on the applied load and, in consequence, is
different for the loaded system measurement and the skim test reading. But for practical reasons, this difference can
be disregarded.
7.6.3 Deceleration method
a) Remove the tyre from the test surface while running at a speed greater than test speed.

b) Record the deceleration of the test drum, Δω /Δt , and that of the unloaded tyre, Δω /Δt (see 8.1.5).
Do 0 To 0
The speed range for measurement includes the test speed and does not exceed 10 km/h above and 10 km/h
below the test speed.
The measured value includes the bearing and aerodynamic losses of the wheel, the tyre, and the drum losses
which are also to be considered.
NOTE It is known that the spindle and drum bearings friction depends on the applied load and, in consequence, is
different for the loaded system measurement and the free deceleration. But for practical reasons, this difference can
be disregarded.
The speed range of the rolling resistance measurement with loaded tyre shall respect the same condition as
for the parasitic losses measurement as described above.
7.7 Allowance for machines exceeding σ criterion
m
The steps described in 7.4 to 7.6 shall be carried out one time if the measurement standard deviation,
determined as described in 10.3.3, is not greater than 0,075 N/kN for passenger car and smaller truck
and bus tyres and not greater than 0,06 N/kN for larger truck and bus tyres. If the measurement standard
deviation exceeds this criterion, the measurement process shall be repeated n times as described in 10.3.3.
The rolling resistance value reported shall be the average of the n measurements.
8 Data interpretation
8.1 Determination of parasitic losses
8.1.1 General
The laboratory shall perform the measurements described in 7.6.2 for force, torque and power methods
or 7.6.3 for deceleration, in order to precisely determine the tyre spindle friction, the tyre and wheel
aerodynamic losses, the drum (and eventually engine and/or clutch) bearings friction and the drum
aerodynamic losses, in the test conditions (load, speed, temperature). The parasitic losses, F , related to the
pl
tyre and drum interface, expressed in newtons, shall be calculated from the force F , torque, power or the
t
deceleration, as shown below.
8.1.2 Force method at tyre spindle
Calculate F using Formula (1):
pl
 rLp
FFpl  tp 1 (1)
 
R
 
where
F is the tyre spindle force in newtons (see 7.6.2);
tp
r is the distance from the tyre axis to the drum outer surface under steady state conditions, in
Lp
metres;
R is the test drum radius, in metres.

8.1.3 Torque method at drum axis
Calculate F using Formula (2):
pl
T
tp
F = (2)
pl
R
where
T is the input torque in newton metres as determined in 7.6.2;
tp
R is the test drum radius, in metres.
8.1.4 Power method at drum axis
Calculate F using Formula (3):
pl
36, VA
pp
F  (3)
pl
U
n
where
V is the electrical potential applied to the machine drive, in volts;
p
A is the electric current drawn by the machine drive, in amperes;
p
U is the test drum speed, in kilometres per hour.
n
8.1.5 Deceleration method
Calculate the parasitic losses, F , in newtons, using Formula (4):
pl
I   I   
D D0 T T0
F   (4)
   
pl
   
Rt Rt
 0  r  0 
where
I is the test drum inertia in rotation, in kilogram metres squared;
D
R is the test drum surface radius, in metres;
Δω is the test drum angular speed increment, drum without tyre, in radians per second;
D0
Δt is the time increment chosen for the measurement of the parasitic losses without tyre, in
seconds;
I is the spindle, tyre and wheel inertia in rotation, in kilogram metres squared;
T
R is the tyre rolling radius, in metres;
r
Δω is the tyre angular speed increment, unloaded tyre, in radians per second.
T0
8.2 Rolling resistance calculation
8.2.1 General
Calculate the rolling resistance using the values obtained by testing the tyre to the conditions specified in
this document and by subtracting the appropriate parasitic losses, F , obtained according to 8.1.
pl
8.2.2 Force method at tyre spindle
The rolling resistance, F , in newtons, is calculated using Formula (5):
r
 rL
FFrt 1 Fpl (5)
 
R
 
where
F is the tyre spindle force, in newtons;
t
F represents the parasitic losses as calculated in 8.1.2;
pl
r is the distance from the tyre axis to the drum outer surface under steady-state conditions, in
L
metres;
R is the test drum radius, in metres.
8.2.3 Torque method at drum axis
The rolling resistance, F , in newtons, is calculated using Formula (6):
r
T
t
F F (6)
r pl
R
where
T is the input torque, in newton metres;
t
F represents the parasitic losses as calculated in 8.1.3;
pl
R is the test drum radius, in metres.
8.2.4 Power method at drum axis
The rolling resistance, F , in newtons, is calculated using Formula (7):
r
36, VA
F  F (7)
r pl
U
n
where
V is the electrical potential applied to the machine drive, in volts;
A is the electric current drawn by the machine drive, in amperes;
U is the test drum speed, in kilometres per hour;
n
F represents the parasitic losses as calculated in 8.1.4.
pl
8.2.5 Deceleration method
The rolling resistance, F , in newtons, is calculated using Formula (8):
r
I  RI  
D v T v
F   F (8)
   
r pl
   
Rt t
  R  
v v
r
where
I is the test drum inertia in rotation, in kilogram metres squared;
D
R is the test drum surface radius, in metres;
Δω is the test drum angular speed increment, loaded tyre, in radians per second;
v
Δt is the time increment chosen for measurement, in seconds;
v
I is the spindle, tyre and wheel inertia in rotation, in kilogram metres squared;
T
R is the tyre rolling radius, in metres;
r
F represents the parasitic losses as calculated in 8.1.5.
pl
NOTE Annex B gives guidelines and practical examples to measure the moments of inertia for the deceleration
method.
9 Data analysis
9.1 Rolling resistance coefficient
The rolling resistance coefficient C is calculated by dividing the rolling resistance by the load on the tyre
r
using Formula (9):
F
r
C = (9)
r
L
m
where
F is the rolling resistance, in newtons;
r
L is the test load, in kilonewtons.
m
9.2 Temperature correction
If measurements at temperatures other than 25 °C are unavoidable (only temperatures not less than 20 °C
nor more than 30 °C are acceptable), then a correction for temperature shall be made using Formula (10):
F = F [1 + K (t – 25)] (10)
r25 r t amb
where
F is the rolling resistance at 25 °C, in newtons;
r25
F is the rolling resistance, in newtons;
r
K is equal to:
t
0,008 for passenger car tyres;
0,010 for smaller truck and bus tyres;
0,006 for larger truck and bus tyres;
t is the ambient temperature, in degrees Celsius.
amb
9.3 Drum diameter correction
Test results obtained from different drum diameters may be compared by using Formula (11) (theoretical):

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