1. Changing the coefficient of mutual contact of a friction pair composed of a sintered iron-graphite material and a steel affects the operating conditions of the pair. Increasing the value of Km to unity is accompanied by a deterioration in the service performance of sintered iron-graphite materials under endfriction conditions at speeds of 11–50 m/sec and loads to 0.5–1 kg/cm2. 2. Profiling the operating surface of the sintered ring substantially decreases the value of Km and improves the conditions of operation of an end-friction pair, 3. The coefficient Km is an important characteristic of end-friction pairs, which should be taken into account together with other service parameters.