Patent ID: 6336485
Filing Date: 2002-01-08
Classification: B60C

Abstract:
A pneumatic radial tire comprising; a radial carcass of at least one ply toroidally extending between a pair of bead cores, each bead core embedded in a bead portion, a belt reinforcing a tread portion on an outer periphery of the carcass, and a row of multiple blocks having different lengths along a circumference of a ground contact region under a pitch variation defined in a tread rubber of the tread portion by at least two straight main grooves extending along the circumference of the ground contact region and a plurality of lateral sub-grooves extending between the mutual main grooves at an inclination angle of less than 90Â° with respect to the circumference of the ground contact region, in which the block row satisfies a relationship of &phgr;L>&phgr;S of an inclination angle (&phgr;) of an edge of the block along the sub-groove with respect to a straight line passing through a top of an acute angle portion of the block and perpendicular to an equatorial plane of the tire wherein, &phgr;L is an inclination angle of a long-pitch block and &phgr;S is an inclination angle of a short-pitch block, wherein said block satisfies a relationship of &agr;L>&agr;S of an inclination angle (&agr;) of each block wall face along both the straight main grooves with respect to a normal line of the tire passing through an edge of the block perpendicular to the ground contact region and wherein, &agr;L is an inclination angle of a block wall face in a block having a longer surface length and &agr;S is an inclination angle of a block wall face in a block having a shorter surface length.