Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Engineering Science and Mechanics


Stability analysis results for the classical bicycle vehicle model are reviewed. New analytical lateral stability relationships for three additional vehicle models are developed. The first model, the extended bicycle model, incorporates x-direction acceleration, tractive forces and aerodynamic drag. The analysis of this model shows the effects of steer angles and tractive effort on lateral stability. The second model, the roll freedom model, includes suspension effects. The effects that springs, shock absorbers, center of gravity height, and roll steer coefficients have upon lateral stability are demonstrated. The third model, the spread tire model, has the tires located away from the vehicle's longitudinal center line. This model illustrates the effects related to individual tire properties, steering geometry and vehicle symmetry;Examples based on actual automobiles are presented to demonstrate the application of these stability relationships and evaluate a variety of design considerations. The extended bicycle model examples compare the results associated with understeer, oversteer and neutral steer vehicles. The effects of various combinations of roll steer coefficients and combinations of springs and shock absorbers are shown from examples using the roll freedom. Examples from the spread tire model are compared and shown to be in ageement with those from the extended bicycle model. In addition, the spread tire model is used to demonstrate the effects of steering geometry and tire mixtures on vehicle stability. The results associated with the various models generally conform with driving experience.



Digital Repository @ Iowa State University,

Copyright Owner

Paul Malone Moldenhauer



Proquest ID


File Format


File Size

228 pages