Preload (rolling bearing)

In order to increase the rigidity or running accuracy of a bearing arrangement using rolling bearings, a negative operating clearance is required for various applications. This means that a preload is required for the bearings. Depending on the bearing type, a distinction is made between axial and radial preload. Axial cylindrical roller bearings and axial ball bearings can only be preloaded axially. Due to their design, cylindrical roller bearings can only be preloaded radially. Single-row angular contact ball bearings and tapered roller bearings are often installed with one or more bearings as sets and are also preloaded. Deep groove ball bearings with internal clearance C3 are also generally installed with axial preload.

Preload refers to the axial load applied to the rolling elements in the bearing to ensure that they remain in contact with the raceway under operating conditions and do not exhibit axial movement. Axial preload can be created by tightening a bearing nut to a defined tightening torque. In other applications, springs, washers or spacers are used to maintain a constant axial preload. There are also rolling bearings that are already preloaded, e.g. for angular contact ball bearings in the universal design, the most common variants that can be ordered are a light and a medium preload.

If the bearings are correctly preloaded, greater rigidity is achieved and therefore less elastic deformation in a certain load range than with non-preloaded bearings. Low-noise running is also achieved, as the lower the operating clearance of the bearing, the better the balls or rollers are guided in the unloaded zone. The correct preload is crucial to ensure optimum bearing performance. Too little preload can lead to axial play, while too much preload can lead to excessive friction and premature wear. It is important to consider the requirements of the specific application and follow the bearing manufacturer's advice where appropriate.