for tires in the United States, in addition to standards for rim dimensions, tubes, valves and other components.
Two standard tests for measuring rolling resistance exist as SAE recommended practices—SAE J1269, “Rolling Resistance Measurement Procedure for Passenger Car, Light Truck, and Highway Truck and Bus Tires” (SAE, 2006) and SAE J2463, “Stepwise Coastdown Methodology for Measuring Tire Rolling Resistance” (SAE, 1999). Both tests are conducted in a laboratory with the tire loaded against a 1.7-meter-diameter drum. While these test procedures are not identical to each other or to on-road operating conditions, they can be expected to provide good relative measures of rolling resistance.
Since precedent and test procedures exist, the government could add grading requirements for rolling resistance to the UTQGS (Uniform Tire Quality Grading System) if there is promise of its effectiveness. At least two barriers exist:
Consumer acceptance—Although the UTQGS was designed to assist consumers in making informed choices when buying passenger car tires, it is not universally effective. The effectiveness was evaluated in a 1992 telephone survey of individuals who buy tires for their own vehicles and individuals who buy tires for fleets of vehicles (Weiss, 1992). Approximately 80 percent of potential customers considered UTQGS information important to a purchase decision, although only about 30 percent of recent customers considered it in their last purchase. More than 50 percent of fleet buyers considered UTQGS information important in buying decisions.
Retread tires—More than 50 percent of the tires on long-haul trucks are retreads. A retread is simply new tread molded on to an existing, pre-used tire carcass. Rolling resistance depends both on the design and materials of the tread stock as well as the underlying structure. Thus, each retread will have a different rolling resistance value. Therefore, it is less practical to expect rolling resistance values to be measured for retread tires than for those produced by OEM tire manufacturers.
Finding 5-9. There is a precedent for government to establish performance measures for tires as illustrated by the Uniform Tire Quality Grading System (UTQGS) adopted by NHTSA in 1980 [Part 575.104 of the Consumer Information Regulations]. The UTGS applies to passenger car tires and requires manufacturers to grade new tires for tread wear, wet traction and temperature resistance. Tread wear is graded on a numerical scale, while traction and temperature resistance are graded on an alphabetic scale. There is no current requirement for grading rolling resistance, or for grading truck tires.
Recommendation 5-9. DOE, EPA, and DOT should arrange to gather and report information on the influence of individual truck tires on vehicle fuel consumption; to convey such tire information to both buyers and sellers; and to periodically reassess the effectiveness of this consumer information and the methods used for communicating it.
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