Vehicle Handling and Control Following Front Ball Joint Failure

Following many accidents, one of the involved vehicles is found with partial or total separation of one of its wheels. In many such cases, forensic evidence on the wheel, and/or on some surface struck by the wheel, provide direct evidence that the wheel separation resulted from the impact. However, in some cases such direct evidence is not as obvious or cannot be identified. In those cases, it is often asserted that before the accident occurred one of the involved vehicles might have undergone a sudden loss of control as a result of a spontaneous partial or total wheel separation.

This paper examines the response of rear wheel drive vehicles when there is a failure involving a ball joint on the front suspension as the vehicle is traveling along a roadway. The design of the front suspension is analyzed to determine the expected effects of such failure on the wheel geometry and on the interaction between the tires and the pavement. Next some case studies of accidents involving wheel loss are examined. Finally, the results of a series of tests are discussed in which ball joint failures are caused to occur as the vehicle is being driven. The effect of these failures on vehicle handling and control is described and compared with the predictions from the design analysis. Finally, the physical evidence left on the vehicle and roadway by the failures is described.