Heavy load pneumatic radial tire

摘要

A heavy load pneumatic radial tire having a tire tread sectioned into a plurality of circumferentially continuous ribs by a plurality of circumferentially extending wide main grooves. One of the ribs disposed at the outermost side when the tire is mounted on a vehicle is provided with a narrow groove circumferentially continuously formed in a proportion of 10% to 40% with respect to a width of the outermost rib from an adjacent tread end. The narrow groove separates the outermost rib into two portions. One of the ribs disposed at the innermost side when the tire is mounted on a vehicle is provided with a discontinuous narrow groove circumferentially disposed in a proportion of 10% to 50% with respect to a width of the innermost rib from an adjacent tread end. This discontinuous narrow groove is composed of circumferentially extending groove portions separated from each other by discontinuous portions each having a circumferential length not shorter than 20% but not longer than 50% of a circumferential length of each of the circumferentially extending groove portions.