Patent ID: 7478657

Claim:
A pneumatic tire having a tread surface having a plurality of main grooves extending straight in a circumferential direction of the tire, land portions extending in the tire circumferential direction being defined by the plurality of main grooves, the land portions each having a ground contact surface comprising a first circular arc C 1 having a single curvature radius in tire meridian cross section, wherein the ground contact surface of at least the land portion which is located second when counted from the outer side of a vehicle when the tire is mounted thereon, is arranged so as to have the first circular arc C 1 and at least a second circular arc C 2 connected thereto on the vehicle outer side thereof, wherein the circular arc located closer to the vehicle outer side has a smaller curvature radius and is positioned more inwardly away from the tread surface, and wherein the ratio d/D of the depth d, measured from a tread surface, of an intersection of the circular are located closest to the vehicle outer side with a vehicle outer sidewall surface of the second land portion to the groove depth D of the main groove, measured from a wall of the main groove that faces the vehicle outer sidewall surface, is 0.02 to 0.1, such that the vehicle outer sidewall surface of the second land portion has a height that is less than that of the wall of the main groove that faces the vehicle outer sidewall surface of the second land portion, and wherein the ground contact surface of the second land portion has an inner circular arc C 2 ′ connected to the first circular arc C 1 on the vehicle inner side thereof, and a third circular arc C 3 connected to the second circular arc C 2 on a vehicle outer side thereof, and further wherein R 1 >R 2 >R 2 ′>R 3 , where R 1 is the curvature radius of the first circular arc C 1 ; R 2 is the curvature radius of the second circular arc C 2 , R 2 ′ is the curvature radius of the inner circular arc C 2 ′, and R 3 is the curvature radius of the third circular arc C 3 .