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.

23. The expert from EC proposed to strengthen tyre rolling resistance and wet grip performance requirements (GRBP-75-29 and GRBP-75-30). GRBP invited him to submit an official document for consideration at the next session. The experts from Germany and the Netherlands stressed the importance of rolling noise and the need to include it in the scope of the future modifications as well.

24. GRBP noted that the experts from France continued consultations with other laboratories on monitoring of the machine deviation for rolling resistance measurements (GRBP-74-04). GRBP invited experts to provide comments to the authors, with a view to preparing an official document for the next session.