Proposal from the Worn Tyres working group to set the wet grip index threshold at 0.80 for class C1 tyres with a nominal aspect ratio equal to or less than 40, a section width equal to or higher than 235 mm and suitable for speeds equal to or greater than 300 km/h and for class C1 all terrain and special use tyres (see GRBP-75-27, slide 6). The proposal also introduces the kworn factor in a new para. 3 in Annex 9 to address wet grip of C2 and C3 tyres in a worn state (see GRBP-75-26-Rev.1 for concept).
21. The expert of IWG WGWT proposed to add the missing references for the molded standard reference test tyre (SRTT16) in the 03 and 04 series of amendments to UN Regulation No. 117 (ECE/TRANS/WP.29/GRBP/2023/2 and ECE/TRANS/WP.29/GRBP/2023/3). GRBP endorsed these references and noted that they had been already included in ECE/TRANS/WP.29/2023/5 and ECE/TRANS/WP.29/2023/8 which would be considered by WP.29 and AC.1 at their forthcoming session in March 2023.
20. The expert of IWG WGWT presented their proposals for the moulded standard reference test tyre and wet grip of C2, C3, and some clusters of C1 tyres in a worn state (ECE/TRANS/WP.29/GRBP/2022/22, ECE/TRANS/WP.29/GRBP/2022/23, GRBP-76-02 and GRBP-76-05). The expert from ETRTO introduced additional amendments (GRBP-76-24-Rev.1, GRBP-76-33-Rev.1 and GRBP-76-34).
21. GRBP adopted ECE/TRANS/WP.29/GRBP/2022/22, as amended by GRBP-76-05 and GRBP-76-34, subject to the removal of the square brackets, and requested the secretariat to submit it for consideration and vote at the March 2023 sessions of WP.29 and AC.1 as draft Supplement 1 to the 03 series of amendments to UN Regulation No. 117.
22. GRBP adopted ECE/TRANS/WP.29/GRBP/2022/23, as amended by GRBP-76-02, GRBP-76-33-Rev.1, and GRBP-76-24-Rev.1, and requested the secretariat to submit it for consideration and vote at the March 2023 sessions of WP.29 and AC.1 as part of the draft new 04 series of amendments to UN Regulation No. 117.
20. The experts from the Informal Working Group for Wet Grip on Worn Tyres (WGWT) reported on their progress (GRBP-75-27) and presented updated Terms of Reference of IWG WGWT (GRBP-75-28). GRBP adopted the revised Terms of Reference, as contained in Annex III to the session report.
21. GRBP recalled that, at the previous session, it had adopted draft amendments on the procedure and thresholds on wet grip performance for C1 tyres in worn state which was subsequently submitted to WP.29 as draft 03 series of amendments to UN Regulation No. 117 (ECE/TRANS/WP.29/2021/12). To complement the document, the expert from IWG WGWT tabled further amendments (GRBP-75-25-Rev.1). GRBP adopted this proposal and requested the secretariat to submit it for consideration and vote at the June 2022 sessions of WP.29 and AC.1 as part of a new 03 series of amendments to UN Regulation No. 117. The expert from IWG WGWT also presented a concept proposal for addressing wet grip requirements for C2 and C3 tyres in worn state (GRBP-75-26-Rev.1).
22. GRBP agreed to request WP.29 and AC.1 to postpone to their June 2022 sessions consideration of ECE/TRANS/WP.29/2021/12, in order to combine it into a consolidated proposal with the adopted amendments mentioned in the previous paragraph.
| GRBP-75-26/Rev.1 | |
| GRBP-75-27 | |
| WT-44-06/Rev.1 | |
| GRBP-76-02 | |
| GRBP-76-24/Rev.1 | |
| GRBP-76-33/Rev 1 | |
| GRBP/2023/3 | |
| WP.29/2023/8 |