Patent ID: 7861755

Claim:
A pneumatic tire having a tread surface having a center region, the tread surface comprising: a first circumferential groove extending in a circumferential direction of the tire in the center region; a second circumferential groove extending in the circumferential direction of the tire in the center region; a middle rib defined by the first circumferential groove and the second circumferential groove; middle lateral grooves obliquely extending in a widthwise direction of the tire and disposed at predetermined intervals in the circumferential direction of the tire in the middle rib, only one terminal end of each of the middle lateral grooves communicating with one circumferential groove of the first circumferential groove and second circumferential groove; an assistant groove provided between each of adjacent middle lateral grooves, the assistant groove extending in such an inclined manner that an inclination direction thereof with respect to the circumferential direction of the tire is opposite to that of the middle lateral grooves; a lateral narrow groove extending in the widthwise direction of the tire between each of the adjacent middle lateral grooves, the lateral narrow groove being smaller in width than the adjacent middle lateral grooves, the lateral narrow grooves and the middle lateral grooves being alternately disposed in the circumferential direction of the tire in the middle rib; and a block defined by the assistant groove, middle lateral grooves and one circumferential groove, wherein: the middle lateral grooves each include a first inclined groove portion communicating with the one circumferential groove and a second inclined groove portion connected to the first inclined groove portion, the first inclined groove portion having an inclination angle Î± ranging from 35 degrees to 60 degrees with respect to the circumferential direction of the tire, the second inclined groove portion having an inclination angle Î² ranging from 0 degree to 30 degrees with respect to the circumferential direction of the tire; and the assistant groove has opposing terminal ends that communicate with the adjacent middle lateral grooves, one terminal end of the opposing terminal ends of the assistant groove being located at a position ranging from 20% to 30% of a tire-widthwise length of one middle lateral groove of the adjacent middle lateral grooves from the one terminal end of the one middle lateral groove toward a side of the other terminal end of the one middle lateral groove in the widthwise direction of the tire, the other terminal end of the opposing terminal ends of the assistant groove being located at a position ranging from 20% to 30% of a tire-widthwise length of the other middle lateral groove of the adjacent middle lateral grooves from the other terminal end of the other middle lateral groove toward a side of the one terminal end of the other middle lateral groove in the widthwise direction of the tire.