Patent ID: 6079464
Filing Date: 2000-06-27
Classification: B60C,Y10S

Abstract:
A pneumatic tire comprisinga tread portion defined by a tread rubber having a Shore A hardness of not more than 65 degrees at 20 degrees C., the tread portion provided with at least one circumferential row of blocks,the blocks in each row circumferentially divided by lateral grooves and having circumferential edges adjacent to the lateral grooves,each of the circumferential edges having a mean inclination angle of 0 to 60 degrees with respect to the tire axial direction, wherein the mean inclination angle is defined as a straight line drawn between the axial ends of the circumferential edge,sidewalls (9A) of the lateral grooves on one side of the lateral grooves in the tire circumferential direction each comprising a first upper slope (S1U) and a first lower slope (S1D), the first upper slope (S1U) extending from the top of the adjacent block to a first point at a depth h1, while inclining at an angle .alpha.1, the first lower slope (S1D) extending from said first point towards the groove bottom, while inclining at an angle .alpha.2 smaller than the angle .alpha.1,the remaining sidewalls (9B) of the lateral grooves on the other side of the lateral grooves each comprising a second upper slope (S2U) and a second lower slope (S2D), the second upper slope (S2U) extending from the top of the adjacent block to a second point at a different depth h2 than said depth hi, while inclining at an angle .beta.1, the second lower slope (S2D) extending straight from the second point towards the groove bottom, while inclining at an angle .beta.2 smaller than the angle .beta.1, wherein the inclining directions of all the slopes (S1U, S1D, S2U and S2D) are such that the width of each lateral groove decreases radially inward, and all the angles are measured with respect to a normal direction to the block top in a cross section at a right angle to the lateral groove, andwith respect to each of the lateral grooves, in a portion (A) of the lateral groove, the depth h1 is more than the depth h2 but not more than 0.8 times the lateral groove depth, and in another portion (B) of the lateral groove, the depth h2 is more than the depth h1 but not more than 0.8 times the lateral groove depth.