BS ISO 23671:2021 pdf download.Passenger car tyres – Method for measuring relative wet grip performance – Loaded new tyres.
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
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. 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, Passenger car tyres and rims — Part 1: Tyres (metric series)
ASTM E965-96, Standard Test Method for Measuring Pavement Macro texture Depth Using a Volumetric
Technique
ISO 4223-1, Definitions of some terms used in the tyre industry — Part 1: Pneumatic 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 terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://wwwIearopedia.org/
3.1 test run single pass of a loaded tyre over a given test surface
3.2 braking test series of a specified number of test runs (31) of the same tyre repeated within a short time frame.
4 Methods for measuring wet grip index
For the evaluation of the wet grip index (G) of a candidate tyre, the wet grip braking performance of the candidate tyre is compared to the wet grip braking performance of the reference tyre on a straight, wet, paved surface. It is measured with one of the following methods:
— vehicle method consisting of testing a tyre set mounted on a commercialized vehicle;
— test method using a trailer or a tyre test vehicle equipped with the test tyre set.
In case of verification of the wet grip index (G) the same test method used for its declaration shall be used.
NOTE Differently from the previous edition of this document, as far as case of vehicle method is concerned, when the candidate tyre size is significantly different from that of the reference tyre, a direct comparison on the same vehicle may not be possible and the test method using a trailer or a tyre test vehicle can be used.
5 General test conditions
5.1 Track characteristics
The surface shall have a uniform gradient ol nut imire [him 2 % in both longitudinal and lateral directions and shall not deviate 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 and foreign deposits.
It shall be a dense asphalt surface.
The maximum chipping size shall be from 8 mm to 13 mm.
The macro texture depth MTD shall be measured as specified in ASTM E965-96 using the area of the track to be used for the wet grip test and shall be (0,7 ± 0,3) mm.
In order to verify the frictional properties of the surface, the reference tyre shall be used as follows.
a) In case of vehicle method, the texture depth is measured in both lanes where the tyres are going to brake.
The temperature-corrected arithmetic mean of the average braking force coefficients (BFCcurr) of at least six valid measurements of the reference tyre (see Clause 6) shall be not less than 0,57 and not greater than 0,79.BS ISO 23671 pdf free download.
BS ISO 23671:2021 pdf download
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