In engineering applications, the increase of friction loss in bearing systems can seriously affect the structural dimensions of bearing assemblies, leading to the vibration and reliability degradation of ball bearings. To solve this problem, the mechanical behaviors of bearing assemblies with different raceway diameters and rotational speeds were investigated. Thereby, the relationship between friction loss, raceway diameter and rotational speed in ball bearing systems is elucidated. It is worth noting that the mechanical behaviors derived from the nonlinear dynamic approach is more realistic than the quasi-static approach used in previous studies. The results of the study show that the larger the diameter of the ball and the fewer the number of balls, the smaller the total friction loss. In addition, the total friction loss grows slowly initially, but rises sharply with increasing speed. These insights provide valuable guidance in determining the optimum operating conditions and structural design of ball bearings.