Analysis of used tires shows rust formation in the belt by penetration of water, deterioration of the adhesion of steel cord to rubber in the carcass, and also a loss of cord tenacity in the carcass. As a model for the belt, vulcanized T-test adhesion blocks with open cord ends were immersed in warm, salt water (90° C; 5 percent sodium chloride), after which the residual adhesion and rubber coverage were measured. The conclusion is that for a belt material, a good rubber penetration should be sought.

In the carcass the loss of adhesion seems to be the major problem. Thermal aging tests under different aging conditions have been carried out, and a rather large difference between the various products can be observed. Loss of cord tenacity, fretting, apparently is determined by the cord construction. As we have no reliable laboratory testing method available, fleet tests will be decisive in this respect.