TIRE FORCE VARIATION MACHINE

Apparatus for measuring force variations of vehicle tires including a shaft-mounted cylindrical load wheel which is movable to impress a predetermined base load on a rotatably mounted tire and be deflected in response to the variations from such base load due to radial, lateral and/or other force variations in the tire. The load wheel shaft is fixed on a carriage slidable on a frame for movement by driving means toward and away from the tire which is rotatable about an axis fixed relative to the frame. Mechanism is constructed and arranged to secure the carriage rigidly with respect to the frame during the force variation measurement so as to isolate the driving means and/or prevent unwanted movements of the carriage relative to the frame from variations in force exerted by the rotating tire after the base load has been applied.