Abstract Assuming dynamic friction to arise from the shearing and subsequent breaking of distinct bonds between the rubbing members, a general equation is derived for the frictional force which involves the number and average life of the bonds as well as the average time lag between breaking and re-making of a bond at a given site. In the case of friction between rubber and smooth, hard surfaces, the bonds are attributed to local molecular adhesion between rubber and track, both formation and breaking of the bonds being thermally activated rate processes. A theory developed on this basis reproduces the experimental results obtained by Grosch in that the coefficient of friction as function of the velocity has a pronounced maximum. The height of the maximum and the velocity at which it occurs are in semi-quantitative agreement with Grosch's findings.