NASHVILLE, Tenn.—The U.S. government is teaming up with the tire and trucking industries to test truck tires to determine the effects of speed and underinflation on the failure rate. Concerned about an apparent increase in the number of truck tire failures since the repeal of the national 55 mph speed limit in 1995, The Maintenance Council of the American Trucking Associations—in cooperation with the tire industry and the National Highway Traffic Safety Administration—will conduct a controlled test this summer. It will compare the effects of lowered inflation pressure on tires running at 55 mph and at 75 mph.
NHTSA has agreed to provide funding of $100,000, and several tire companies are donating tires and personnel to oversee the test, which will be conducted over a five- to eight-week period starting in mid-June at the Transportation Research Center in central Ohio.
The test will be a step-down procedure, starting with the drive axle and trailer tires inflated to 85 psi. Tire pressures will be dropped 10 psi every 5,000 miles until failure, said Al Cohn, market manager for Goodyear's commercial systems engineering.
There will be four tractor-trailer combinations, two to run at 55 mph and two at 75 mph. The gross vehicle weight will be 90,000 pounds, or 5,000 pounds per axle.
One of each pair of trucks will run on new tires—Goodyear G362 drive tires and Bridgestone R194 trailer tires—and the other on retreads—Goodyear G362 drive and Bandag T4100 trailer. All the test tires will be size 295/75R22.5, and the retreads will be done on ``virgin'' casings—that is, those without repairs.
Each tractor will be equipped with Michelin steer tires, inflated to 100 psi. The tires fitted to replace blown tires will not be included in the evalution.
All tires and retreads will be inspected by X-ray and shearography, courtesy of Michelin, before and after the test.
The test will be conducted only during daylight hours to maximize the effects of heat and to allow the testers to find all the debris whenever a tire fails. The results will be made public at the TMC's fall meeting.