UN R117 — Supplement 3 to the 04 series of amendments

Paragraph 1.1. now says that the Regulation applies to new pneumatic tyres of classes C1, C2 and C3 “in new and worn state with regard to adhesion performance on wet surfaces (wet adhesion)”. Before, the worn state was named only for class C1 tyres. In paragraph 2.11., “a tyre structure designed” is now “a tyre designed”, and in paragraph 2.13.1., “structure” is now “construction”. Paragraph 2.16.1. now defines “principal grooves” as “the wide tread grooves positioned in the central zone of the tyre tread, as defined in Annex 9 to this Regulation”. New paragraph 2.16.2. defines “tread groove” as “the space between two adjacent ribs and/or blocks in the tread pattern”. In Annex 9, paragraph 2.1.3. now says that “groove” means tread groove.

Paragraph 2.18. now refers to F2493 – 24 for SRTT16, F3611 – 24 for “moulded SRTT16 worn”, F3676 – 24 for SRTT17S and F3675 – 24 for SRTT17W. Before, these were F2493 – 23, F3611 – 22e1, F3676 – 23 and F3675 – 23. In Annex 8, the SRTT16 for the ice performance of class C1 tyres must now be stored in accordance with ASTM F2493 – 24. The rim texts in Annexes 6 and 8, paragraph 2.11. and the class C1 footnote now refer to ISO 4000-1:2024, not ISO 4000-1:2021.

Paragraph 6.8. now says that, to be classified as a “professional off-road tyre”, “a special use tyre shall have the following characteristics”, instead of “a tyre shall have all of the following characteristics”. For class C1 tyres, item (a) requires a tread depth ≥ 11 mm, a void-to-fill ratio ≥ 35 per cent and a maximum speed category “less than or equal to 160 km/h (speed category symbol Q)”. New item (b) gives class C2 tyres one characteristic: a maximum speed category “less than or equal to 160 km/h (speed category symbol Q)”. Item (c) gives class C3 tyres one characteristic: a maximum speed category “less than or equal to 110 km/h (speed category symbol K)”. Before, item (a) applied to classes C1 and C2 tyres. Class C3 tyres also needed a tread depth ≥ 16 mm and a void-to-fill ratio ≥ 35 per cent.

New paragraph 2.3.1.6. of Annex 9 covers “Water depth measurement for external watering”. The test track should be watered at least 30 minutes before the water depth is measured, to equalize the surface temperature and water temperature. The water depth device must be “capable to measure a water depth range that is larger than the regulatory defined range of 0.5 mm - 1.5 mm”. “Three measurements shall be recorded for each measuring point throughout the whole testing area”, and the average for each measuring point must be in the range of 0.5 mm - 1.5 mm. The paragraph also gives rules for contact, optical and ultrasonic devices, and the measurement must be performed without wind interference. In Annex 5, paragraphs 3.3. and 1.3., and Annex 9, paragraph 2.3.3., wetting must now be performed “in such a way that the wind does not affect the outcome of the test”.

In Annex 9, the temperature-corrected average braking force coefficient (BFCave,corr) for each braking test must now be “greater than or equal to 0.42 and less than or equal to 0.64”. Before, it had to be not less than 0.4 and not greater than 0.65. The temperature corrected average peak braking force coefficient (µpeak,corr) must now be “greater than or equal to 0.50 and less than or equal to 0.75”, instead of not less than 0.45 and not greater than 0.80. The same new ranges apply to the reference tyre results of the initial and the final braking tests within a test cycle. Under new paragraph 12.27., until 6 July 2026, Contracting Parties “may continue to grant type approvals of class C1 tyres according to the 04 series of amendments to this Regulation, based on the test procedures for measuring the wet adhesion of tyres in worn state as described in Annex 9 to this Regulation using wetted frictional properties of the surface specified in Supplement 2 to the 04 series of amendments to this Regulation”. Under new paragraph 12.28., Contracting Parties “shall continue to grant extensions to existing type approvals of class C1 tyres according to the 04 series of amendments to this Regulation first granted before 7 July 2026” based on the Annex 9 test procedures and the Supplement 2 surface friction, “unless a new test has to be performed on a different representative tyre”.

In Annex 5, Part (B), paragraph 1.1.1. now reads “Standard Reference Test Tyre method” and gives a method that “uses the SRTT16”. In this method, the temperature corrected µpeak,corr must be “greater than or equal to 0.65 and less than or equal to 0.90”. The sentence on the methods by the class of the candidate tyre and the method (trailer or vehicle) is no longer in paragraph 1.1.1. The table of μpeak and BFC ranges by tyre class and SRTT is also no longer in paragraph 1.1.1. As from 1 September 2028, paragraph 12.26. says that Contracting Parties “shall not be obliged to accept type approval issued according to Supplement 2 to the 04 series of amendments to this Regulation, first issued after 31 August 2028, if the track characteristics for measuring wet adhesion of tyre in new state are not established using the following reference tyres”. The words “first issued after 31 August 2028” are new.

In paragraph 6.2.1. and Annexes 5, 6 and 8, limits now read “greater than or equal to” and “less than or equal to” instead of “not less than”, “not greater than” or “not more than”, with the same values. In Annex 5, Part (A), “exceeds 4 per cent” and “higher than 4 per cent” are now “greater than 4 per cent” for the coefficients of variation. In Annex 5, Part (A), paragraph 3.2.2., “at least six (6) valid test runs” is now “at least six (6) test runs”. Annex 7, Appendix 3, Part 1, item 7 no longer refers to paragraph 6.5.1.1. and now reads “Snow grip index SG”.