Presentation on wet grip test issue concerning to use of SRTT_worn for RRT.

Proposal to introduce a procedure and thresholds on wet grip performance for tyres in worn state for C1 tyres as submitted to GRBP by the Worn Tyres working group.

Proposal to maintain the performance stages for the following reasons:

• By removing the performance stages, we would allow two different markings, with and without performance stage indication, for the same actual performance level depending on whether the type approval was granted according the 02 or 03 series of amendments.
• Some countries which are not contracting parties of 1958 Agreement refer to stage 1 and stage 2 of 02 series of amendments of UN Regulation No. 117. Therefore, the removal of the stages would create some ambiguity and misunderstanding of the actual performance of the product.
• The above is even more important for tyre of classes C2 and C3 as they are not affected by the introduction of the performance for the adhesion on wet surfaces for tyres in worn state, and for which the suffix B is not added to the approval marking.

1. In paragraph 5.3.1.2. the wording has been adjusted to the definitions as amended with GRBP/2021/12 proposal to identify adhesion on wet surfaces of tyre in new state.
2. Paragraph renumbered and reworded in line with the text proposed in paragraph 8.3.1. of document ECE/TRANS/WP.29/2021/17.
3. Paragraph 12.2. has been reworded according to the intentions of paragraph 41. of the General Guidelines for United Nations regulatory procedures and transitional provisions in UN Regulations to avoid TAA’s to interpret a mere change in markings as a change introduced by the new SoA.
4. Paragraph 12.6.1. is in line with paragraph V.9bis. of the General Guidelines for United Nations regulatory procedures and transitional provisions in UN Regulations. Proposed paragraph 12.4.1., is introducing date limitations and precise reference to a specific series of amendments and in such does not conform to V.9 bis transitional provisions. Consequently, it should then be deleted from the proposal.
5. In Annex 1, paragraphs 8.2. and 8.3., the reference to non-existent items was removed.
6. In Annex 2 – Appendix 1, Example 1, the wording has been aligned to the other examples provided in Annex 2.
7. In Annex 9, paragraphs 2.1.5 to 2.2.1.2.4.1. have been reworded to clarify the preparation of class C1 tyres in worn state.
8. In Annex 9 – Appendix 1, the example of worn tyre preparation report example has been updated to remove unnecessary and ambiguous data to be reported.
9. In Annex 9, Appendix 2, Example 2, the report example has been updated in line with the proposal of Annex 5, Appendix, Example 2 of document ECE/TRANS/WP.29/GRBP/2021/17.

Worn Wet grip Index equation proposed by ETRTO on 25 October
Questions addressed by WTPP and further assessment
Responses provided by ETRTO provided to WTPP on 8 November
WTPP conclusion