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A newly designed and built Mobile Tire Testing Machine (MTTM) is described that has features for large and continuously variable camber and steering angles with minimum tire scrub. This equipment was used to examine tire properties for six passenger car tires. Of special interest were the tire characteristics at combinations of high slip and camber angle. It was found that camber stiffness decreases with increasing slip angle when the slip and camber angles are both positive, and at limit conditions in slip angle, cambering a tire has little effect on the lateral side force produced. When the slip angle is negative, and the camber angle is positive, preliminary data shows that a greater lateral force is produced when compared to operating at limit conditions in slip angle alone.

A towed tire testing fixture suitable for use in testing all terrain vehicle tires is designed and built. Vertical loads on the tire under test can be varied from 100 to 400 1bf (445-1780N) and the camber and slip angles can be varied from 0 to 20 degrees. In addition, longitudinal slip measurements in braking are possible through the use of a disc brake assembly. Six strain gage loads cells are used to determine the force and moment resultants at the tire contact patch. Data acquisition and processing are done through a Daytronic 10KUD data pack and lap top PC. This system is used to test seven representative ATV tires operating on surfaces of hard packed clay. Two of these tires are also tested on short and tall field grass, and on beach sand. Information on the lateral force coefficient, and the rolling resistance coefficient, as functions of vertical load on the tire, and slip angle of the tire, are generated.