Patent ID: 9561693
Date: 2017-02-07
CPC Classifications: B60C

Claim:
1. A pneumatic tire comprising a tread having a tread surface and being formed with a circumferential direction groove extending along a tire circumferential direction, wherein the circumferential direction groove comprises: a first groove portion formed at a tread road surface side so as to extend along the tire circumferential direction with an amplitude in a tire width direction; and a second groove portion formed at the groove bottom side of the first groove portion so as to extend in a straight line along the tire circumferential direction, wherein a first groove portion groove depth A and a second groove portion groove depth B are set such that A≦B, and wherein a groove width of the second groove portion decreases in a tire radial inner direction continuously from a top of the second groove portion to a bottom of the second groove portion, wherein three of the circumferential direction grooves are provided in the tread and are formed in a zigzag shape, and a central circumferential direction groove of the circumferential direction grooves located between the others of the circumferential direction grooves has a groove width of the second groove portion set wider than a groove width of the second groove portion of the others of the circumferential direction grooves, wherein a groove width in the tire width direction of the first groove portion of the central circumferential direction groove is set greater than a groove width in the tire width direction of the first groove portion of the others of the circumferential direction grooves, while the groove width of the first groove portion minus the groove width of the second groove portion of the central circumferential direction groove is set to be equal to the groove width of the first groove portion minus the groove width of the second groove portion of the others of the circumferential direction grooves, wherein step portions are formed at a groove depth intermediate portion of each of the circumferential direction grooves at a boundary portion of the first groove portion and the second groove portion, and the step portions are substantially parallel to the tread surface.