Preload (engineering)

Advantages of preloading include the following: maintain axial and radial position for accurate displacements of angular movements; increase bearing rigidity; prevent sliding or gyroscope-like movements, especially with high acceleration or rotation rates; maintain relative position of bearing elements.

When tensile specimens are initially placed into testing grips, they can be subjected to small compressive forces.

Establishing a small preload as a part of the test method eliminates those compressive forces on specimens and improves the repeatability of results.

By tensioning, preloading increases the natural frequency of a structure, avoiding resonance due to external disturbances.

In the particular case for bearings and fasteners, preload reduces or cancels backlash or dead zones.