Report on discussions concerning the definition of a specific cluster ‘tyre 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’ by indicating the intended use of such tyres.

Proposal from the Worn Tyres working group 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 (see GRBP-75-27, slide 6). 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).

Proposal from the Worn Tyres working group 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 thee 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.