The radial preload of rolling bearings refers to a method of using interference fit to expand the inner ring of the bearing or compress the outer ring to eliminate radial clearance and keep the bearing in a preloaded state. Cylindrical roller bearings and needle roller bearings can only be subjected to radial preload.

The purpose of radial preload is to increase the number of rolling elements in the load zone and improve the bearing stiffness. In high-speed cylindrical roller bearings, radial preload can reduce the phenomenon of rolling elements and raceways slipping under the action of centrifugal force. For the tapered inner bore bearing in the double row cylindrical roller bearing, a lock nut can be used to adjust the relative position of the inner ring and the adapter sleeve to reduce the radial clearance of the bearing and achieve radial preload.