Pneumatic tire

摘要

A pneumatic tire is provided in the tread portion with zigzag circumferential grooves and axial grooves so that a row of circumferentially arranged blocks is formed on each side of each of the zigzag circumferential grooves. Each of the zigzag circumferential grooves is composed of axially inner and outer circumferential segments and oblique segments. The axially inner and outer circumferential segments are arranged alternately in the tire circumferential direction. The oblique segments connect between the axially inner and outer circumferential segments, whereby the zigzag circumferential groove extends in the form of a trapezoidal wave. The zigzag amplitude is in a range of from 4 to 15% of a half tread width (Tw/2). The width of the zigzag circumferential groove is in a range of from 7 to 13% of the half tread width (Tw/2). The number of the axial grooves connected to each of the zigzag circumferential grooves on both side thereof is in a range of from 8 to 12 when counted in a tire footprint. The axial grooves each have a groove width WY of from 8 to 25% of a pitch length Py between the axial groove and the circumferentially adjacent axial groove.

主权项

1. A pneumatic tire comprising
a tread portion which is provided with zigzag circumferential grooves, axial grooves extending between the zigzag circumferential grooves, and axial grooves extending between the zigzag circumferential grooves and tread edges, so that a row of circumferentially arranged blocks is formed on each side of each said zigzag circumferential groove, wherein each of the zigzag circumferential grooves is composed of axially inner circumferential segments, axially outer circumferential segments and oblique segments, the axially inner circumferential segments and the axially outer circumferential segments are arranged alternately in the tire circumferential direction, the oblique segments connect between the axially inner circumferential segments and the axially outer circumferential segments, whereby the zigzag circumferential groove extends in the form of a trapezoidal wave, the zigzag amplitude measured axially between the widthwise center line of the inner circumferential segments and the widthwise center line of the outer circumferential segments is in a range of from 4 to 15% of a half tread width (TW/2) measured axially between the tire equator and the tread edge, the width of the zigzag circumferential groove is in a range of from 7 to 13% of said half tread width (TW/2), the number of the axial grooves connected to each said zigzag circumferential groove on both sides thereof is in a range of from 8 to 12 when counted in a footprint of the tire, the axial grooves are connected to the circumferential segments at the respective intermediate positions of the lengths of the circumferential segments and not connected to the oblique segments, the axial grooves each have a groove width WY in a range of from 8 to 25% of a pitch length Py between the axial groove and the circumferentially adjacent axial groove, and each of the axial grooves has a U-shaped cross-sectional shape along the length thereof wherein the groove bottom is a semicircle.