BS ISO 23671:2021 pdf free
BS ISO 23671:2021 pdf free.Passenger car tyres — Method for measuring relative wet grip performance — Loaded new tyres.
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 of not more than 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 (BFCcorr) 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.
