Automotive suspension geometry describes the kinematic movement of a car's suspension based on a theoretical analysis of measured or designed points. This geometric analysis can be done with pencil and paper on a drawing board or with simple physical models, but is more commonly analyzed by the means of specialized software. By contrast, Kinematics and Compliance (K&C) machines measure suspension parameters as loads are applied to an existing chassis and vehicle suspension.
This paper will compare the two approaches as applied to a stock car racing chassis. Significant agreement between the theory and measurement will be demonstrated. Significant differences such as tire deflection will be explained. Additional differences due to compliance of “solid” parts will be described.
The paper will also describe suspension parameters which can be measured directly, such as camber and toe, and those which must be calculated, such as caster, kingpin and, instant centers. It will also compare kinematic analysis with force-based analysis and show how K&C force measurements relate to both.