Proposal to amend GRBP-83-32-Rev.1 to ensure robust tyre abrasion measurements regardless of test method used. Amendments modify paragraph 6.1 to require test facilities demonstrate equivalence per Annex 4 procedure; insert paragraphs 12.8 and 12.9 deeming inter-facility campaign participants equivalent for C₁ tyres and allowing pre-regulation test data through 1 July 2028; insert Annex 3 paragraph 1.4 requiring inter-facility equivalence assessment; amend Annex 3 paragraph 2.8 with abrasion calculation equations including transfer function coefficient; insert test report items 1.1–1.4 in Appendices 2 and 6; and insert new Annex 4 establishing equivalence demonstration procedure for vehicle and indoor drum test facilities.

Proposal to amend document GRBP-83-32-Rev.1 to renumber Paragraph 6.1. as 6.1.1., renumber current Paragraph 6.1.1. as 6.1.2., introduce new paragraph 1.4. to Annex 3 Introduction, amend paragraph 2.8. with detailed abrasion index and level calculation equations, renumber items in Appendix 2, delete item 1.3. from Appendix 2, and amend item 1.3. in Appendix 6 to clarify transfer function applicability between circuit and drum test facilities.

JATMA submitted this position on the draft UN Regulation for tyre abrasion at GRBP-83-54. JATMA requests adoption of the indoor drum test method under conditions equivalent to the vehicle test method for type approval. JATMA proposes that the Generic transfer function coefficient should be 1.14, calculated excluding tyre code 127 which exhibits significant variation. JATMA also proposes that the abrasion index range for tyres used in the Annex 4 procedure should be set between 0.4 and 0.5, and that no restrictions should be imposed on baseline test facilities when applying the Specific Transfer Function.

This status report documents the Tyre Abrasion Task Force’s progress toward finalizing a draft UN Regulation on tyre abrasion for C1 tyres, as presented to GRBP 83 Part II. The task force pursued three workstreams: data analysis to reduce method uncertainty and inversion risk, editorial improvements to increase clarity of the draft regulation, and development of a method equivalence solution. GRBP 83 Part I achieved consensus on limit values and introductory dates but could not reach consensus on equivalence procedures between convoy and drum methods. Six informal documents (GRBP-83-32-Rev.1, GRBP-83-48-Rev.1, GRBP-83-49, GRBP-83-50-Rev.1, GRBP-83-53, and GRBP-83-55) addressing equivalence methodology, drum specifications, and code of practice frequency were submitted for potential adoption at the extraordinary GRBP 83 Part II session.