Patent ID: 8267133

Claim:
A pneumatic tire having a tread surface, a plurality of main grooves extending in a circumferential direction of the tire in the tread surface, land portions being defined by the plurality of main grooves, the land portions having at least one land portion between two adjacent main grooves, a circumferential groove less in width than the main grooves extending in the tire circumferential direction in the at least one land portion, wherein; lateral grooves are disposed in the at least one land portion at prescribed intervals in the tire circumferential direction, the lateral grooves extending from each main groove adjacent to the at least one land portion to the circumferential groove; a plurality of blocks are defined by the main grooves, circumferential groove and lateral grooves; sub-grooves are disposed in each block at a prescribed interval in the tire circumferential direction, the sub-grooves extending from the main groove to at least a midway of the block in the tire width direction; at least three block portions are defined by the sub-grooves in the tire circumferential direction; the at least three block portions have widths different from each other in the tire width direction, whereby the main groove adjacent to the each block has a variable width; the at least three block portions have groove wall surfaces facing the main groove, the groove wall surface of a block portion less in width having a greater inclination angle with respect to a tread normal direction; a difference between the width of a block portion of the at least three block portions which is the least in width and the width of a block portion of the at least three block portions which is the greatest in width is 1 mm to 4 mm; and wherein the sub-grooves comprise three sub-grooves extending to the midway of the block, and wherein four of said block portions are defined by the three sub-grooves in the tire circumferential direction.