Optimization of Suspension Geometry for Enhanced Lateral Grip

by Karl Bumstead

Submitted : Spring 2018

This research examines the front suspension geometry of General Motors’ 1983-2004 four-wheel drive S-series and models possible solutions for improving the camber curve by increasing the effective spindle height. Achieving a taller effective spindle height is accomplished by the use of a 1” taller upper ball joint in both models and modifying the lower ball joint mount on the other model to inverse the direction that the ball joint mounts; this adds 3” to the effective spindle height, adding in the taller upper ball joint for a total of a 4” increase to the effective spindle height compared to the stock model. In both models, it was essential to increase the length of the upper control arm to compensate for the height differences of the spindles. The modeling of these solutions was accomplished by using a two-dimensional suspension modeling software with measurements taken off of an unmodified frame, control arms, and spindles for a four-wheel drive 2000 GMC Jimmy.

The data obtained from the suspension software was then used as inputs for a curve generating software that was able to create rational functions that follows the models with coefficient of determination (r2) of 0.994 or higher. These functions then were derived and graphed, as well as computing the arc length for further analysis. The results of both solutions were relevant; by increasing the effective spindle height by 1”, the model generated a more effective camber curve for a vehicle that is driven on both the street and the race track; by increasing the effective spindle height by 4”, the model generated a more effective camber curve for a vehicle that is only track driven, as the aggressiveness of the camber curve would result in excessive tire wear under normal street driving circumstances. The intended use of the vehicle will determine which model should be applied, with both of them offering enhanced lateral grip with varying levels of compromise.

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