Patent ID: 9636952
Date: 2017-05-02
CPC Classifications: B60C

Claim:
1. A heavy duty pneumatic tire comprising: a tread portion provided with a plurality of circumferentially and continuously extending zigzag shaped main grooves, a plurality of land portions separated by the main grooves, and a plurality of lateral grooves to form a plurality of block elements on each land portions, each land portion comprising a number of pitches in a range of from 40 to 50, wherein each pitch consists of one block element and one lateral groove adjacent to the concerned block element, each block element having a circumferential length in a range of from 85% to 95% of a circumferential length of the pitch, and the main grooves comprising at least one crown main groove arranged nearby a tire equator, at least one shoulder main groove arranged nearby a tread edge, and at least one middle main groove arranged between the crown main groove and the shoulder main groove, wherein the middle main groove has a zigzag amplitude larger than those of the crown main groove and the shoulder main groove, the middle main groove comprises axially innermost protruding portions and axially outermost protruding portions, the lateral grooves comprise a plurality of axially inner middle lateral grooves extending axially inwardly from the axially innermost protruding portions of the middle main groove and a plurality of axially outer middle lateral grooves extending axially outwardly from the axially outermost protruding portions of the middle main groove, the tread portion is further provided with a plurality of first groove bottom sipes and a plurality of second groove bottom sipes, and each of the first groove bottom sipes extends from a bottom of the middle main groove to a bottom of one of the axially inner middle lateral grooves and each of the second groove bottom sipes extends from the bottom of the middle main groove to a bottom of one of the axially outer middle lateral grooves, and wherein the first groove bottom sipes and the second groove bottom sipes are alternately arranged in a circumferential direction of the tire without communicating with each other at the axially innermost protruding portions of the middle main groove.