Effect of Tie Rod Length Variation on Bump Steer

Steering and suspension system has to be designed properly to achieve improved handling characteristics. Improper design of steering systems will result in steering errors such as bump steer and roll steer. These steering errors results in reduced steering performance. During the design of steering system the tie rod length has to be properly selected to reduce these steering errors. The purpose of the work is to analyze the effects of tie rod length variation on bump steer. Multi body dynamic model of the selected vehicle was created using MSC ADAMS Car software. Ideal design of steering system to achieve zero bump steer was created. The tie rod length was later varied up to 10% to study the effect of varying length on bump steer. Parallel wheel travel analysis was conducted to study the tie rod length variation on bump steer. Acceleration test was conducted on a flat road having bump to analyze the effect of changing tie rod length on steering performance of the vehicle. The test results were obtained for toe, bump steer, steer force and assist angle with 5% and 10% length variations. For 5% variation, steer assist angle was lower with 0.007deg./mm bump steer. For 10% length variation, bump steer exceeded up to 0.03 deg. /mm with greater steer assist. The results with 5% variation indicated lower bump steer as well as lesser steer assist within the acceptable range. With 10% variation, bump steer and steer assist was much higher with increased steering efforts.