The first outcome of this investigation is that non-proportionality between sliding abrasion and load has relatively little effect on the load dependence of tire wear, which is almost entirely governed by the load dependence of the contact length, unless the inflation pressure is very low. The modified theory on the wear of slipping wheels predicts near proportionality at constant slip between wear in crab walk and side force. This relation is useful for test procedures and has been qualitatively confirmed by experiment. The theory suggests, furthermore, the existence of a severity effect on tire wear ratings which is independent of ambient or tire temperature and is expected to affect the wear rating of different tires if road tests are carried out on test routes with radically different surface topology.