Abstract: A method of and apparatus for adjusting the preload of an anti-friction bearing is disclosed. A compressive load is applied to the opposite transverse faces of the outer races of a linear bearing by hydraulic or pneumatic cylinders. While the bearing assembly is held in compression, a test force is applied to one end of the inner race or slide in a direction parallel to its constrained direction of travel to cause the slide to move through the bearing at a steady rate of travel. While the slide is in motion, rolling friction characteristics are measured by a force gauge. The resulting force gauge measurement corresponds to a particular bearing preload.