Patent ID: 8813800

Claim:
A pneumatic tire comprising a tread portion provided on each side of the tire equator with a center main groove and an axially outer shoulder main groove each extending continuously in the tire circumferential direction so that the tread portion is divided into a center land portion between the center main grooves, a pair of middle land portions between the center main grooves and the shoulder main grooves, and a pair of shoulder land portions axially outside the respective shoulder main grooves, wherein the center main grooves are each formed by circumferentially-connected arc groove pieces each comprising an arc portion curved so as to swell toward the tire equator, and the center main grooves each have a zigzag shape and a zigzag amplitude of from 2% to 5% of a tread width of the tread portion, the middle land portions are each provided with middle inclined grooves so as to circumferentially divide the middle land portion into middle blocks, and the middle inclined grooves each extend axially outwardly from one of intersection portions of the arc groove pieces of the adjacent center main groove to the adjacent shoulder main groove at an angle of from 12 to 30 degrees with respect to the tire circumferential direction so that a tip end angle of a land portion sandwiched between each middle inclined groove and the center main groove is in a range of from 30 to 75 degrees, and the width of each middle inclined groove is gradually decreased toward the axially outside of the tire, the shoulder main grooves are each formed by circumferentially-connected curved groove pieces each curved so as to swell toward the tire equator, and the shoulder main grooves each have a zigzag shape and a zigzag amplitude larger than those of the center main grooves, and the middle blocks are each provided with a first middle auxiliary groove extending from the adjacent arc groove piece of the center main groove to the adjacent shoulder main groove and a second middle auxiliary groove extending from the adjacent curved groove piece of the shoulder main groove to the adjacent middle inclined groove, so that the middle block is divided into a first portion on a tire equator side, a third portion on a tread edge side, and a second portion therebetween, said second portion is divided into an inner part on a tire equator side and an outer part on a tread edge side by a third middle auxiliary groove extending from said first middle auxiliary groove to said adjacent curved groove piece, and said outer part and said third portion have ground contacting areas whose difference is not more than 30% of the smaller one of them.