IMPROVED TREAD FOR HEAVY GOODS VEHICLE TYRE

摘要

Tread for heavy goods vehicle tyre with total thickness E and total volume V, this tread having at least one continuous groove (2) comprising: - at least two wear layers I, II in the thickness of the tread, each layer having a thickness at most equal to 75% of the total thickness E of the tread, - a plurality of external cavities (21) and a plurality of internal cavities (22) positioned radially and wholly inside the tread surface (11) in the as-new condition, each internal cavity being connected to an external cavity by a connecting duct, this tread having a total groove volume Vc at least equal to 7% and at most equal to 12% of a volume equal to the sum of the total volume V and of the total grooves volume, and this tread also having an effective grooves volume Ve for each wearing layer that is less than the total grooves volume Vc, this effective grooves volume satisfying the following relationship: 0.4 St < Ve < 0.8 St, in which 0.4 and 0.8 are heights expressed in millimetres and St is the surface area bounded by the external contour of the contact patch of the tread measured under static conditions with customary pressure and loading, and furthermore this tread being such that at least the first wearing layer I consists of a rubber compound based on at least one material having a dynamic Tg - measured in accordance with standard ASTM D 5992-96, higher than -40°C and containing a predominant proportion of SBR copolymer with a Tg > -65°C.