Tire Operational and Sustainability Trade-Offs

In 2012 the Sustainable Worldwide Transportation Consortium at the University of Michigan Transportation Research Institute (UMTRI) funded a forecast of likely changes in tire sustainability through 2025, as a result of feasible tire evolution. This paper is a synopsis of the resulting report, "Tire Operational and Sustainability Tradeoffs'' [Reference 5], completed in late summer 2013. In it results are expressed in terms of fuel amount, distance, and weight commonly used in the United States rather than in SI units or in terms used in the underlying mandated goals such as grams of CO2 per mile (light vehicles) or grams per load-ton per 100 miles (medium and heavy vehicles) because of the underlying regulatory framework (Unit conversions to SI are found in the Appendix). The forecast fuel-economy change is the primary factor considered in evaluating tire sustainability. The secondary factor considered is the change in raw material usage, which affects tire weight. The changes are predicted for the five vehicle power plants now in use: gasoline, diesel, hybrid, plug-in hybrid, and battery electric. Vehicles from class A to class E plus pickup trucks are analyzed. This is done with consideration of expected changes in vehicle weight. Tire sizes that are likely to be used, as the vehicles change, are estimated. It is possible that operational trade-offs may preclude tire changes that are desirable in terms of sustainability. To this end, probable vehicle ride and handling effects along the different possible tire-evolution paths are assessed. Aspects of ride that are considered are harshness, modal frequencies, and in-vehicle noise. Cornering in the ordinary driving range, stopping, and the limits of cornering are examined as aspects of handling. Effects on dry, wet, and snowy surfaces are considered. The conclusion reached is that the best tire technical path to follow from now until 2025 is to use higher-aspect-ratio tires operating at higher cold-inflation pressures, provided that any negatives in ride and handling can be overcome in vehicle design. Styling questions are not considered in the report, but it is noted that these could be an important problem, since the tires on the technically desirable path will not have the appearance to which customers have been accustomed in recent years.