An Analytical Model for the Transient Rolling Resistance Behavior of Tires

The rolling resistance of tires has received increased attention as automakers and consumers seek to improve fuel economy. Standard rolling resistance tests are currently performed to characterize steady state rolling resistance. The transient rolling resistance behavior is also of interest, but requires more elaborate and more expensive testing. This paper presents a theory to predict the transient response of rolling resistance to changes in velocity, from empirical data generated at steady state. The current model neglects the effect of changes in inflation pressure. A general relationship is derived for an arbitrary velocity history. The special case for instantaneous velocity histories is investigated. The model is then compared with experimental results. Finally, we use the model to predict transient rolling resistance results for coast down testing, and a simulated urban driving cycle. The model provides a simple and effective way to determine transient tire rolling resistance from steady state test results. This may reduce the need for transient testing in the future.