Proposal to amend Annex 5, part (B) of UN R117. Changes include replacing “Average Deceleration (AD)” with “braking force coefficient (BFC)” terminology throughout paragraphs 2.2.2.1., 2.2.2.7.1., 2.2.2.7.2., and 2.2.2.7.3. Paragraph 2.2.2.3. is amended to clarify terminology regarding vertical static test load and load capacity. Paragraph 2.2.2.7.4. is deleted. Paragraphs 2.2.2.7.5. through 2.2.2.8.4. are renumbered and amended to align the wet grip test method for C2 and C3 tyres with changes made to the passenger car test method and ISO 15222:2025.

Proposal to supersede GRBP/2025/28, consolidating amendment proposals from GRBP/2025/28, GRBP-82-27, GRBP/2026/6, and GRBP-83-20-Rev.2. Changes include moving tyre abrasion provisions to a separate UN Regulation, deleting paragraphs 5.7 to 5.10 and Annex 10, updating ASTM standard references to F2872-25, F2871-25, and F3678-25, amending Annex 5 part (b) paragraph 1.1.1., and deleting paragraph 2.21. defining abrasion performance terms.

ETRTO measurement uncertainties reduction efforts for UN R117 rolling sound emission test methods are progressing through outdoor and indoor Round Robin tests. Eight of thirteen outdoor test centres have completed tests for C₁ and C₂ tyres; remaining centres anticipate completion by mid-year. Indoors, two of six ETRTO test centres completed tests with others expected finished by mid-year. An intermediate report with available data will be presented in September 2026, full results postponed to February 2027, and the Working Document with test method evolution now expected in September 2027 instead of February 2027.

Proposal to amend paragraph 2.18. to update Standard Reference Test Tyre definitions to ASTM International standards: E1136-19 for SRTT14, F2493-24 for SRTT16, F2872-25 for SRTT16C, F2871-25 for SRTT19.5, F2870-23 for SRTT22.5, F3678-25 for SRTT19.5 siped, and F3677-23 for SRTT22.5 siped. Also amend paragraph 12.21. to accept existing type approvals and grant extensions to class C₃ tyres using either SRTT19.5 or SRTT22.5 before 1 September 2028, and use SRTT19.5 siped or SRTT22.

The GOIE on Tyre Noise Level Alignment in UN R117 targets reducing dispersion of measurements for tyres of Class C1 and C2 and investigating possibility to develop a test method with an SRTT as reference. An intermediate report will be presented to GRBP in September 2026, with a Working Document proposing evolution of the test method by September 2027. Five meetings have been held with 13 test centres from France, Japan, Netherlands, Spain and ETRTO. Eight of thirteen test centres have completed tests on 15 C1 and 5 C2 Japanese market tyres, with completion targeted for mid-2026.

The secretary reported on C1 tyre testing activities. The Netherlands and Germany noted potential delays in Normal tyre testing at high temperature by end of March due to temperature conditions. The co-chair presented a status report for GRBP’s 83rd session, which the group approved. Future meetings are scheduled for February through April.