Individual toe measuring system

Abstract

An apparatus and method is disclosed which utilizes modified wheel aligner heads and which accomplishes measurement of individual wheel toe on a vehicle having a pair of non-steerable rear wheels and a pair of steerable front wheels. The apparatus and method provides measurement of a steering or a rolling direction for the front and the rear wheel pair as a result of optical measurements taken relating the orientation of the planes of the wheels to the centerline of the vehicle chassis. Once the steering direction of the front wheels is obtained, individual toe measurements for the front wheels may be made relative to the chassis centerline. Alternatively, once the steering or average rolling direction of the rear wheels is obtained individual toe measurements for the rear wheels may be made relative to the chassis centerline and individual toe measurements for the front wheels may be made relative to the rear wheel rolling direction. Neutral steering of the front wheels may thus be made to coincide directionally with the rear wheel rolling direction. The optical measurements are made with an aimable viewfinder utilizing contrarotating plano prisms which are monitored in rotational position to provide data utilized in calculating wheel pair steering direction and correction factors for the measurements taken by the aligner heads.