National foreword

This British Standard is the UK implementation of ISO 23671:2021. It supersedes BS ISO 23671:2015, which is withdrawn.

The UK participation in its preparation was entrusted to Technical Committee AUE/4, Tyres and wheels for motor vehicles.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2021.

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing this document is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

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 documents 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).

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions 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 Technical Committee ISO/TC 31, Tyre, rims and valves.

This third edition cancels and replaces the second edition (ISO 23671:2015), which has been technically revised.

The main changes compared to the previous edition are as follows:

the method accuracy and reproducibility has been improved by updating the formulae and coefficients for wet grip index calculation;
the method of track validation has been revised to be done only with 16 in SRTT instead of with BPN or 14 in SRTT,
the wet grip performance measurement using a control tyre in case of vehicle method has been withdrawn.

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.

1 Scope

This document specifies the method for measuring relative wet grip braking performance index to a reference under loaded conditions for new tyres for use on passenger cars on a wet-paved surface.

The methods developed are meant to reduce variability. The use of a reference tyre is necessary to limit the variability of the testing procedures.

This document applies to all passenger car tyres except for:

special-use tyres marked with "ET";
T-type temporary spare tyres;
tyres fitted with additional devices to improve traction properties (e.g. studded tyres).

2 Normative references

3 Terms and definitions

4 Methods for measuring wet grip index

5 General test conditions

5.1 Track characteristics

5.2 Wetting conditions

5.3 Atmospheric conditions

6 Measurement of tyre wet grip index on a commercialized vehicle

6.1 Principle

6.2 Equipment

6.3 Conditioning of the test track

6.4 Test speed measurement requirements

6.5 Tyres, rims and fitment on vehicle

6.6 Procedure

7 Measurement of tyre wet grip index on a trailer or a tyre test vehicle

7.1 Principle

7.2 Test apparatus

7.3 Selection and preparation of test tyres

7.4 Preparation of test track and apparatus

7.5 General test conditions

7.6 Procedure

Bibliography

BS ISO 23671:2021

Passenger car tyres. Method for measuring relative wet grip performance. Loaded new tyres

Current

Published:

30 Jun 2021