Proposal to delete obsolete footnotes concerning worn tyre wet grip and approvals under UN R117 coincident with approvals under UN R54. The 04 series of amendments to UN R117 introduces the requirements on adhesion of tyres in worn state on wet surfaces for tyres within the scope of UN R54.

1. Proposal to amend the 04 and 05 series of UN R41 and the 02 series of UN R63 to allow use of the latest state of the art ISO 10844 test track.
2. ISO has updated the ISO 10844 standard to reduce track-to-track variability caused by differing interpretations and implementations of the technical requirements. The tyre/road contribution to the overall sound performance of a motorcycle is lower compared to cars.
3. The improvements from the ISO 10844:2014 to the 2021 version would not result in a need for updating the surface for L-category test tracks: Updating the ISO 10844 reference would have negligible impact on the measurement procedure and measurement results.
4. If however the ISO reference in the L-category noise regulations would be updated without maintaining the current ISO 10844:2014 as an option, IMMA sees a potential risk of tracks needing recertification, creating administrative burden with no practical benefit.
5. If later on, the tracks would need re-surfacing anyway (e.g. due to wear), then these can be built and certified according to ISO10844:2021. Because of the above, IMMA would like to allow certification with the tracks complying to either ISO10844:2014 or ISO10844:2021.
6. This proposal takes the opportunity to introduce proposals for additional corrections in R41/04 and R41/05 as specified below:
   • Supplement 9 to the 04 series of amendments to UN Regulation 41 introduced a new paragraph 12.4, needing to renumber the (former) paragraphs 12.4 to 12.9 (WP.29/2021/4). Due to this renumbering, the reference to paragraph 12.7 in Annex 6 footnote a, and Annex 7 paragraph 2.6 is no longer correct and should be replaced by a reference to paragraph 12.8.
   • With the introduction of the 05 series of amendments the Transitional Provisions were rewritten and footnote a of Annex 6 became obsolete.

Proposal to introduce measures to reduce variability across assessments and to bring the latest ISO 10844 standard test surface into the Regulation. The proposal includes editorial corrections and clarifications based on the 03 series of amendments to UN R51 up to Supplement 7 (GRBP/2023/12) subject to review and approval during the January 2023 GRBP session.

Proposal to bring the latest ISO 10844 standard test surface into the Regulation.

Proposal to introduce provisions to allow the type approval of special use tyres that fulfil the requirements for snow performance as laid out in Annex 7, to bring the latest ISO 10844 standard test surface into the Regulation, and to make editorial corrections.

Proposal to introduce provisions to allow type approval of special use tyres that fulfil the requirements for snow performance as laid out in Annex 7, to improve precision of the test procedures for measuring the wet adhesion of tyres in a worn state by using a moulded SRTT16 reference tyre (instead of a buffed tyre), to introduce new transitional provisions related to this change, to extend corrections already made to the 02 series to the 03 series and make additional editorial corrections, and to define the range for tyre inflation vis-à-vis rim size to reduce uncertainties in measuring tread depth. The proposal introduces the tyre reference F3611-22 per document GRBP/2023/2 submitted to the January 2023 session of GRBP.

Proposal to revise the limits for rolling resistance and wet grip, to address tyres for vintage vehicles, to revise the definition for special-use C1 tyres, and 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. The proposal also introduces the k_worn 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), provisions to allow the type approval of special use tyres that fulfil the requirements for snow performance as laid out in Annex 7, and a new definition of traction elements to characterize traction tyres.