Assessment of tire technologies and practices for tire wear and energy use reduction

Andrew Burke and Marc Melaina, University of California-Davis, Institute of Transportation Studies

Keywords

tires, rolling resistance, tire pressure, fuel economy, wear, nitrogen inflation

Abstract

Various aspects of the effects on tire usage and markets of new laws and regulations in the United States and California are analyzed and discussed. Special attention is given to the effects on tire rolling resistance and maintenance as they relate to vehicle fuel economy and tire wear. Detailed data are given on the rolling resistance of tires especially those classified as low rolling resistance tires with a rolling resistance coefficient (RRC) less than .008. Vehicle simulation results indicated that vehicle fuel economy will increase by 1.5 % for a 10 % reduction in RRC. Hence if the RRC is reduced from .01 to .008, a fuel economy increase of about 3 % would be expected. The price, RRC, and mileage life trade-offs are technology dependent and difficult to assess. Both rolling resistance and mileage life are critically dependent on tire maintenance especially proper tire inflation. It was found that a 6 psi under-inflation (about a 17 % deviation from the correct value of pressure) results in a 10 % increase in RRC which would result in a 1.5 % reduction in fuel economy for the vehicle. Tire pressure monitoring systems are available that display to the driver both the pressure and temperature of the tires on the vehicle and alert the driver if there is a problem with one or more of the tires. The use of these monitoring units should result in both safer and more efficient vehicle operation. Another approach that is being considered to improve tire performance and life is to utilize nitrogen inflation rather than air. Little meaningful data are available to evaluate with confidence the effect of nitrogen inflation on tire performance, especially tire pressure and temperature. An analysis of the properties of air and nitrogen as they relate to tires indicate that only the permeability of rubber varies significantly for the two inflation gases.

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