公开(公告)号：JPS60116508A

公开(公告)日：1985-06-24

申请号：JP22451283

申请日：1983-11-30

Applicant: BRIDGESTONE CORP

Inventor： TOKUNAGA SEIICHIROU ,  IKEDA NOBUTADA

IPC: B60C11/00 ,  B60C11/04 ,  B60C11/11

Abstract: PURPOSE:To improve resistance to rolling and resistance to abrasion in all seasons by forming a tread part of the captioned tire, to be used for a bus and the like for heavy load, into a compound tread with an upper part rubber of predetermined hardness and a lower part rubber of predetermined hardness and loss tangent. CONSTITUTION:The layer 5 of tread rubber is formed by the layer 6 of an upper part rubber in the radial outward direction and the layer 7 of a lower part rubber in the radial inward direction. Said layer 6 is made of a cap rubber of JIS hardness below 75 deg. at -20 deg.C, while said layer 7 is made of a base rubber of JIS hardness above 54 deg. at 100 deg.C and loss tangent below 0.22 at 50Hz, 25 deg.C and 2% strain. The upper part rubber 6, forming an independent block 12 with four main grooves and a lateral groove 9, is formed in such a manner as a block pattern is formed for a new product, and after abrasion of the tread, it is changed into a rib pattern which leaves a scraped part 9b as a notch. Thus, resistance to rolling and resistance to abrasion can be improved in all seasons.