Pneumatic radial tyre

摘要

A pneumatic radial tyre comprises a breaker-belt (7) disposed radially outside a carcass (6), and a band-belt (9) disposed radially outside the breaker-belt (7) and having organic fibre cords laid substantially parallel with the tyre equator. In the meridian section of the tyre mounted on a standard rim and inflated to 0.5% of standard inner pressure, the tread (2S) has a triple radius profile and the band-belt (9) has a variable ply number (N1,N2,N3) accommodated to the triple radii R1,R2,R3) of the tread. The tread profile is composed of a central part (Y1) of a radius R1, a pair of middle parts (Y2) of a radius R2, and a pair of shoulder parts (Y3) 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.