Method and apparatus for reducing lateral force variations and

Abstract

A method and apparatus for reducing lateral force variations and overturning moment variations in pneumatic tires by detecting the magnitude, direction and location of such variations and alternatingly grinding off opposite portions of the two shoulders of the tire tread. A tire is mounted on a test rim, inflated to operating pressure, and rotated under a normal service load against a loading drum. Force variations in the lateral and radial directions are detected and measured by load cells operatively associated with the drum axle and located at opposite ends of the axle. The sum of the lateral force variation forces or the difference of the radial force variation forces measured by the load cells provides a voltage level signal representative of the direction, magnitude and location of the lateral force variation and the overturning moment variation. The phase angle of this signal is ascertained to determine the location on the tire of these variations. Where these variations exceed a preset level, they are reduced by alternatingly grinding a zone of one shoulder of the tire tread and the opposite zone of the other shoulder of the tire tread in response to the phase angle of the variation signals. Reduction of lateral force variations by this method also reduces radial force variation.