The influence of heat, developed in process, on the performance of bearings applied in rotational systems is often studied. In the present work, the influence of thermal expansion on the reduction of the radial clearance after assembly and the dynamics of the self-aligning ball bearing are experimentally studied. The course of the temperature change in the interior and exterior of the bearing was measured for several values of the radial clearance (RIC) and different rotational speeds. The results show a correlation between the temperature difference inside and outside the bearing and the clearance. Furthermore, it demonstrates the importance of the precise alignment of the clearance, as it was accepted.