A Technical Analysis of a Proposed Theory on Tire Tread Belt Separation-Induced Axle Tramp 2011-01-0967

Recently, papers have been published purporting to study the effect of rear axle tramp during tread separation events, and its effect on vehicle handling [1, 2]. Based on analysis and physical testing, one paper [1] has put forth a mathematical model which the authors claim allows vehicle designers to select shock damping values during the development process of a vehicle in order to assure that a vehicle will not experience axle tramp during tread separations. In the course of their work, “lumpy” tires (tires with rubber blocks adhered to the tire's tread) were employed to excite the axle tramp resonance, even though this method has been shown not to duplicate the physical mechanisms behind an actual tread belt separation.

This paper evaluates the theories postulated in [1] by first analyzing the equations behind the mathematical model presented. The model is then tested to see if it agrees with observed physical testing. Finally, the validity of the physical test methods are evaluated. Among the issues of concern were the discovery of significant algebraic and mathematical errors, questionable assumptions in the modeling of the suspension system, and procedurally flawed physical testing. This study found that the results from the referenced analysis and testing are invalid. Review of U.S. government analysis and conclusions further prove that no relationship exists between the purported suspension system damping levels and crash statistic where a tread separation is involved.