Bearing Pre-load is defined as:
Internal stress to a bearing through application of negative clearance is known as bearing pre-loading.
What is mean when you hear: No Bearing Pre-load Allowed
There is no clearance and no negative clearance of an installed bearing surface.
This does not include any intended spring pressure from a supporting mechanical source for the bearings’ operating purpose.
Ex: A Concentric Slave Cylinder (CSC), Hydraulic Release Bearing (HRB) or external slave cylinder may have a spring as part of the mechanical operation which in turn operates a bearing.
This intended spring pressure is not considered pre-load or negative clearance of an installed bearing. In this example pre-load can be applied by having more pressure than what the spring provides.
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