1. Field of the Invention
This invention relates to pneumatic radial tires, and more particularly to a pneumatic radial tire which can suppress local wear of tire tread due to lateral forces produced in the cornering or the like of the tire.
2. Related Art Statement
For instance, in the tire mounted on a front wheel shaft of a vehicle, wear of an outward tread portion at the mounted state is faster as compared with that of the other portion due to the lateral force produced in the cornering. Thus, uneven wear begins to occur in such a fast worn portion as the tire goes on, and finally the durable life of the tire becomes shortened.
As a countermeasure for solving the problem of the abovementioned uneven wear, there have been attempted a method of controlling the rigidity distribution of tread rubber by changing the tread pattern or the kind of rubber used, a method of controlling the lateral force in the cornering by changing the outer profile of the tread, and the like. However, the effect of preventing uneven wear can not be maintained up to the last stage of the tire life by these methods, so that the conventional techniques do not come to fundamentally solve the above problem.
Furthermore, the technique for solving the problem of uneven wear is disclosed in U.S. Pat. No. 4,214,618 and EP-A-19,070. However, these techniques have problems on the thickness of the sidewall portion near the shoulder of the tread and the formation of a recess with respect to the tread width, and particularly they are not sufficient to prevent uneven wear due to the lateral force in the cornering.
In any case, it is particularly important to eliminate the deviation of the wearing rate in the tread surface starting from the initial stage of the running for fundamentally preventing the occurrence of uneven wear.