Usually the stiffness of a rolling element bearing increases with increased bearing load. The reason is the increase of contact area. Is this always the case?
If a bearing under pretension is loaded radially, the bearing stiffness can decrease with increased radial load. The reason is the contact area again, which will be decreased as the load for some rolling elements will decrease. Following diagram shows the axial and radial stiffness of a 6204 deep groove ball bearing without clearance. The axial load is 500N and the stiffness first decreases with increased radial load. For large radial loads the stiffness will increase again after the rolling elements opposite to load direction are unloaded. The load distribution for a radial load of 0N, 1500N and 3500N is additionally shown in the diagram.
The decrease of stiffness would be larger if a bearing with clearance would be used.