Citation

No Author(s) Listed. Transp. Res. Board Spec. Rep. Ser. 2006; (286): 1-174.

Copyright

(Copyright © 2006, National Academy of Sciences USA)

DOI

unavailable

PMID

unavailable

Abstract

Each year Americans spend about $20 billion replacing the tires on their passenger cars and light trucks. Although passenger tires last far longer today than they did 30 years ago, most are replaced every 3 to 5 years because of wear. A total of about 200 million replacement passenger tires are purchased in the United States annually. Each time they replace their tires, motorists spend several hundred dollars and must choose among tires varying in price, style, and many aspects of performance. The tires they do buy will affect not only the handling, traction, ride comfort, and appearance of their vehicles but also fuel economy. Tires affect vehicle fuel economy mainly through rolling resistance. As a tire rolls under the vehicle's weight, its shape changes repeatedly as it experiences recurring cycles of deformation and recovery. In the process, mechanical energy otherwise available to turn the wheels is converted into heat and dissipated from the tire. More fuel must be expended to replace this lost energy. Combinations of differences in tire dimensions, design, materials, and construction features will cause tires to differ in rolling resistance as well as in many other attributes such as traction, handling, noise, wear resistance, and appearance. Once they are placed in service, tires must be properly maintained to perform as intended with respect to all attributes. The maintenance of proper inflation pressure is especially important. The collective outcomes of the choices consumers make when they buy tires are matters of public interest. The 220 million passenger cars and light trucks in the United States consume about 130 billion gallons of motor fuel annually. Finding ways to reduce this energy consumption is a national goal for reasons ranging from ensuring economic and national security to improving local air quality and reducing greenhouse gas emissions. Maximizing the wear life of tires is also important from the public standpoint of controlling the population of scrap tires that can burden landfills and recycling programs. While the handling, traction, and other operating characteristics of tires are of particular interest to tire buyers, they are also matters of broader public interest inasmuch as they may influence the safety performance of vehicles on the nation's highways. This study was conducted at the request of Congress with funding from the National Highway Traffic Safety Administration (NHTSA). It examines the rolling resistance characteristics of passenger tires sold for replacement and how differences in rolling resistance relate to other tire attributes. Specifically, Congress asked the National Research Council (NRC) to assess the feasibility of reducing rolling resistance in replacement tires and the effects of doing so on vehicle fuel consumption, tire wear life and scrap tire generation, and tire operating performance as it relates to motor vehicle safety. Congress asked that the assessment include estimates of the effects of reductions in rolling resistance on consumer spending on fuel and tire replacement. To conduct the study, the Transportation Research Board, under the auspices of NRC, assembled a committee of experts in tire engineering and manufacturing, mechanical and materials engineering, and statistics and economics. The study committee reviewed the technical literature and analyzed data on passenger tire rolling resistance and other characteristics. Many aspects of tire design, construction, and manufacturing are proprietary, which limits the availability of quantitative information, particularly on the effects of specific changes in tire design and construction to reduce rolling resistance. Nevertheless, enough quantitative and technical information exists in the public domain to assess and reach some general conclusions about the feasibility of reducing rolling resistance in replacement tires and the implications for other tire attributes. Effects on consumer spending on fuel and tire replacement can also be approximated. The study findings and conclusions are summarized below. Taken together, they persuade the committee that the influence of passenger tires on vehicle fuel consumption warrants greater attention by government, industry, and consumers. A recommendation for congressional action is offered in light of this conclusion.