ISO/FDIS 15222

ISO/DISFDIS 15222
ISO/TC 31
Secretariat: ANSI
Date: 20242025-08-0221
Truck and bus tyres — Method for measuring relative wet grip
performance — Loaded new tyres
Pneumatiques pour camions et autobus — Méthode de mesure de l'adhérence relative sur revêtement mouillé
— Pneumatiques neufs en charge
DISFDIS stage
Warning for WD’s and CD’s
This document is not an ISO International Standard. It is distributed for review and comment. It is subject to change
without notice and may not be referred to as an International Standard.
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 supporting documentation.

ISO/DISFDIS 15222:2025(en)
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ii
ISO/DISFDIS 15222:2025(en)
Contents
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Methods for measuring wet grip . 4
5 General test conditions . 5
6 Measurement of tyre wet grip on a standard vehicle . 7
7 Test method using a trailer or a tyre test vehicle . 14
Annex A (informative) Example test reports of wet grip index . 20
Bibliography . 24

iii
ISO/DISFDIS 15222:2025(en)
Foreword
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This document was prepared by Technical Committee ISO/TC 31, Tyres, rims and valves.
This third edition cancels and replaces the second edition (ISO 15222:2021), which has been technically
revised.
The main changes are as follows:
— theaddition of new reference tyres in Clauses 5.4, 6.7.4, 7.8.3C3 SRTTs 19.5, and Annex A22.5 siped have
been added;;
— revision of the track characterization method in Clause 5.1has been updated.
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.
iv
ISO/DISFDIS 15222:2025(en)
Truck and bus tyres — Method for measuring relative wet grip
performance — Loaded new tyres
1 Scope
This document specifies the method for measuring the relative wet grip braking performance index to a
reference under loaded conditions for new tyres for use on commercial vehicles on a wet-paved surface.
NOTE The methods developed in this document are intended to reduce variability. The use of aA reference tyre is
necessaryused to limit the variability of the testing method procedures.
This document applies to all commercial vehicle, truck and bus tyres.
This document does not apply to:
— tyres fitted with additional devices to improve traction properties (e.g. studded tyres);
— professional off-road tyres.
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.
ASTM E965-15, Standard Test Method for Measuring Pavement Macrotexture Depth Using a Volumetric
Technique
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 23671, Passenger car tyres — Method for measuring relative wet grip performance — Loaded new tyres
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
test run
single pass of a loaded tyre over a given test surface
3.2
candidate tyre
T
test tyre that is part of an evaluation programme
ISO/DISFDIS 15222:2025(en)
3.3
reference tyre
R
standard reference test tyre (3.19)) that is used as a benchmark in an evaluation programme
Note 1 to entry: These tyres usually have carefully controlled design features to minimize variation.
3.4
control tyre
C
intermediate tyre that is used when the candidate tyre (3.2)) and the reference tyre (3.3)) cannot be directly
compared on the same vehicle
3.5
braking force
longitudinal force between a tyre and the road resulting from braking torque application
Note 1 to entry: It is expressed in newtons.
3.6
braking force coefficient
BFC
ratio between the average deceleration in a test run (3.1)) and the acceleration gravity (9,81
−2
m∙s )
3.7
dynamic tyre braking force coefficient
µ(t)
ratio between the braking force (3.5)) and the vertical load (3.10))
acquired in real time
3.8
peak braking force coefficient
µpeak
maximum value of the dynamic tyre braking force coefficient (3.7)) that
occurs prior to the lockup of a wheel (3.9)) as the braking torque is progressively increased
3.9
lockup of a wheel
condition of a wheel in which its rotational velocity about the wheel spin axis is zero and it is prevented from
rotating in the presence of applied wheel torque
3.10
vertical load
normal force (Z-direction) of a tyre exerted on the road resulting from the mass supported by the tyre
Note 1 to entry: It is expressed in newtons.
3.11
trailer
tyre test vehicle
special purpose tyre evaluation vehicle which has instruments to measure the vertical and longitudinal forces
on one tyre during braking
ISO/DISFDIS 15222:2025(en)
3.12
hitch height
coupling height
height when measured perpendicularly from the centre of the articulation point of the trailer towing coupling
or hitch to the ground, when the towing vehicle and trailer are coupled together
Note 1 to entry: The vehicle and trailer shall be standing on level pavement surface in their test mode complete with the
appropriate tyre(s) to be used in the particular test.
3.13
braking test
series of a specified number of test runs (3.1)) of the same tyre repeated within a short time frame
3.14
braking test cycle (3.18)
series of braking tests (3.5)) that consist of an initial braking test of the reference tyre (3.3)) set, of up to three
braking tests of either candidate tyre (3.2)) sets or control tyre (3.4)) sets, or both, and a final braking test of
the same reference tyre set (3.17)) or
3.15
vehicle method
method for testing a tyre mounted on a commercially available vehicle
3.16
trailer or a tyre test vehicle method
method for testing a tyre mounted on a trailer towed by a vehicle, or mounted on a special tyre test vehicle
3.17
tyre set
four or six tyres depending on the test vehicle
3.18
tyre set
one or two tyres
3.19
SRTT
standard reference test tyre
tyre that is produced, controlled and stored under specific conditions, in order to be used as a reference tyre
for testing
Note 1 to entry: These tyres usually have carefully controlled design features to minimize variation. The requirements
for SRTTs are given in ASTM international standards as indicated in the following subclauses  to (3.19.1 to ) . (3.19.6:)
3.19.1
SRTT16C
[1]
standard reference test tyre (3.19)) as defined in ASTM F2872
Note 1 to entry: It has the designation 225/75R16C 116/114S.
3.19.2
SRTT19.5
[2]
standard reference test tyre (3.19)) as defined in ASTM F2871
Note 1 to entry: It has the designation 245/70R19.5 136/134M.
ISO/DISFDIS 15222:2025(en)
3.19.3
SRTT22.5
[3]
standard reference test tyre (3.19)) as defined in ASTM F2870
Note 1 to entry: It has the designation 315/70R22.5 154/150L.
3.19.4
SRTT16
[4]
standard reference test tyre (3.19)) as defined in ASTM F2493
Note 1 to entry: It has the designation P225/60R16 97S.
3.19.5
SRTT19.5 siped
[5]
standard reference test tyre (3.19)) as defined in ASTM F3678
Note 1 to entry: It has the designation 245/70R19.5 136/134M SW.
3.19.6
SRTT22.5 siped
[6]
standard reference test tyre (3.19)) as defined in ASTM F3677
Note 1 to entry: It has the designation 315/70R22.5 154/150L SW.
3.20
Classclass of tyre
type of tyres intended to be used on similar vehicles
[7]
[SOURCE: ISO 20908 ]]
3.20.1
class C2 tyre
commercial vehicle tyres with the Load Indexload index (LI) in single formation lower than or equal to 121
and speed category symbol higher than or equal to "N"
[8]
Note 1 to entry: speedSpeed symbol “N” is defined in ISO 4209-1 the ISO 4209-1.
3.20.2
class C3 tyre
commercial vehicle tyres with the Load Indexload index (LI) in single formation lower than or equal to 121
and speed symbol "M" and below, or such tyres with the Load Index (LI) in single formation 122 and higher
[8]
Note 1 to entry: speedSpeed symbol “M” is defined in the ISO 4209-1 ISO 4209-1.
4 Methods for measuring wet grip
The relative wet grip braking performance of a loaded new tyre for commercial vehicles travelling straight
ahead on a wet, paved surface can be measured by one of the following methods:
— a vehicle method consisting of testing a tyre set mounted on a standard vehicle;
— a test method using a trailer or a tyre test vehicle equipped with a test tyre set.
ISO/DISFDIS 15222:2025(en)
5 General test conditions
5.1 Track characteristics
5.1.1 General
The surface shall be a dense asphalt surface with a uniform gradient of not more than 2 %. The surface shall
not deviate by more than 6 mm when tested with a 3 m straight edge.
The test surface shall have a pavement of uniform age, composition and wear. The test surface shall be free of
loose material or foreign deposits.
The maximum chipping size shall be from 8 mm to 13 mm.
The macro texture depth (MTD) of the area of the track to be used for the wet grip test shall be measured as
specified in ASTM E965-15, and shall be (0,7 ± 0,3) mm.
The surface friction value for the wetted track shall be established by either of the following methods:
a) method specified in 5.1.2;;
b) method specified in 5.1.3,, according to the class of candidate tyre and the method, i.e. trailer (5.1.3.1)) or
vehicle (5.1.3.2););
The determined wetted surface friction value shall be within the range indicated in Table 1.
Table 1 — Frictional properties of the surface
Class of candidate tyre SRTT Trailer method Vehicle method
μpeak
...