Abstract: A wheel alignment system uses head units attached to each of the four wheels. The front head units contain photodetector arrays which view across the front of the vehicle and to the rear. The rear units carry photodetector arrays which look forward. Each photodetector array views a target on one of the other head units. A microcomputer in each head unit determines an angular value based upon the position of the target image on the photodetector array. The angle values determined by the microcomputers of the individual head units are supplied to a master computer in a main console which determines individual toe angles with respect to a tread centerline for either the front two wheels or for all four wheels. The master computer controls a display at the main console, as well as a remote display to guide the mechanic in making alignment adjustments.