Effects of Tire Structure and Operating Conditions on the Distribution of Stress Between the Tread and the Road

Between the tread of the tire and the road there are distributions of interfacial pressure and horizontal stresses that affect many of the important operating properties of pneumatic tires. Among these are traction, treadwear, steering forces, noise generation, power loss, and envelopment properties. These distributions of pressure and stress are determined by the internal structure of the tire, the inflation, the load, and the operating conditions. The paper describes some of the relationships obtained from experimental studies. These same distributions also serve as clues of mechanical processes that take place within the structure of the tire. From these data we observe such matters as (1) the relationship of the lateral gradient of the interfacial pressure to the overturning moment and to the lateral walkout of the tire; (2) the mechanics of the rib to rib offset of the fore and aft shears in free rolling and steered tires; (3) the lateral stress distribution as affected by crown structure, the compressive spreading effects and the sidewall structure; (4) the dependence of the lateral pressure gradients on the characteristics of the sidewall; and (5) the effects of the above on the traction ratios (regional slip zones).