<p> The paper analyzes components of the cam profile of the camshaft in the ‘D-240’ internal combustion engine, the requirements placed on the friction couple consisting of the cam profile and the tappet liner. The scope of study included a review of dimensions of constituent parts of the inlet and outlet cam profiles, as well as their individual features. The study enabled making a method for calculating the contact width and area, the degree of slippage, as well as the wear rate of the profile of inlet and outlet cams operating in the lubricating medium, with an account of the roughness and oil film thickness in the contact area of the friction couple. The resulted analytical dependences allowed us to determine the influence of the normal load, angular velocity, slip rate, contact width, yield strength of the material on the wear rate of cam profiles. </p>