Normally, bearings are used with a slight internal clearance under operating conditions. However, in some applications, bearings are given an initial load, which means that the bearings’ internal clearance is negative before operation. Typical reasons and applications for preloading bearings are:

● To maintain bearings in an exact position in both the radial and axial directions and to maintain the running
accuracy of the shaft.
● To increase bearing rigidity. This is often needed on the main shaft of machine tools or the pinion shaft of
automobile differentials.
● To minimize noise due to axial vibration and resonance.
● To prevent sliding due to the gyratory movement of rolling elements.
● To maintain the rolling elements in their proper position with the bearing rings.