Pneumatic radial tire with band-belt and triple radius tread profile

Abstract

A pneumatic radial tire comprises a breaker-belt disposed radially outside a carcass, and a band-belt disposed radially outside the breaker-belt and having organic fiber cords laid in substantially parallel with the tire equator. In the meridian section of the tire which is mounted on a standard rim and inflated to 0.5% of a standard inner pressure, the tread has a triple radius profile and the band-belt having a variable ply number accommodated to the triple radii of the tread such that the number of plies throughout more than sixty percent (60%) of the axial width of the parts of the tread having the first, second and third radii of curvature, respectively, are different from each other. The tread profile is composed of a central part of a radius R1, a pair of middle parts of a radius R2, and a pair of shoulder parts of a radius R3. For example, the ply number N1 in the central part is 0, the ply number N2 in the middle parts is 1, and the ply number N3 in the shoulder parts is 2.