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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.

This paper is the second one of a series of papers describing the All Terrain Vehicle “Trim Model”. The development of a four-wheeled ATV trim model is presented in this paper. Vehicle parameters such as the effect of a gear differential and an anti-roll bar on the understeer, neutral steer, oversteer characteristics were examined. The results were compared with the experiments and it was found that the trim solution was in close agreement with the experimental data.

This paper describes the steady-state handling characteristics of three-wheeled All Terrain Vehicles (ATVs). A mathematical model, called the trim model which is based on the balance of forces and moments, has been developed for the dynamic analysis of the ATVs under steady, constant-radius turns. A numerical technique known as the continuation method has been used to solve the nonlinear simultaneous equations derived from the trim model. It is shown that the handling characteristics of an ATV are very different from those of an automobile. An ATV has a tendency to tip over under tight radius turns and should be handled with care. We believe that the results of this study can be used to design an ATV with improved handling characteristics.