Patent ID: 7784510
Filing Date: 2010-08-31
Classification: B60C,Y02T

Abstract:
1. A heavy duty tire comprising: a carcass that extends from a tread portion to each of bead cores of bead portions through sidewall portions; a belt layer which comprises a plurality of belt plies including a widest belt ply having a maximum width and which is disposed radially outward of said carcass in said tread portion; a pair of belt cushion rubbers having an approximately triangular cross section and a maximum thickness at a location corresponding to each of axially outer ends of said widest belt ply, each of said belt cushion rubbers having a Shore A hardness of 60 to 70, each of said belt cushion rubbers being interposed between said carcass and an axially outer end portion of said belt layer so as to have a gradually decreasing thickness as the belt cushion rubber extends from said axially outer end portion of said belt layer along a radially outer surface of said carcass, and a radial distance between the axially outer end of said widest belt ply and a radially inner end of the corresponding belt cushion rubber is from ⅓ to ¾ times a radial distance between the axially outer end of said widest belt ply and a location where the tire width reaches a maximum; a pair of sidewall rubbers each disposed in each of said sidewall portions and having a radially outer end which extends radially outward beyond a lateral base line drawn in an axial direction of the tire from the axially outer end of said widest belt ply to cover the axially outer end of said tread rubber; and a tread rubber disposed radially outward of said belt layer in said tread portion, the tread rubber including: wherein, on said lateral base line, the La/Lt ratio of a thickness La of said base rubber layer to a distance Lt from the axially outer end of said belt ply having the maximum width to the outer surface of the tire is from 0.6 to 0.8, the Lb/Lt ratio of a thickness Lb of said cap rubber layer to said distance Lt is from 0.1 to 0.3, and the Ls/Lt ratio of a thickness Ls of said sidewall rubber to said distance Lt is from 0.1 to 0.2, on a normal line extending from the axially outer end of said belt ply having the maximum width to the tread outer surface, the Ta/Tt ratio of a thickness Ta of said base rubber layer to a distance Tt from the axially outer end of said belt ply having the maximum width to the tread outer surface is from 0.35 to 0.45, and the Cb/Tb ratio of a thickness Cb of said cap rubber layer in a tread center region, the center line of which is the equator of the tire and which has a width of 50% of the tread width, to a thickness Tb of said cap rubber layer on said normal line is more than 1.0 and less than 1.6.