HILTON HEAD ISLAND, S.C.-Ford Motor Co. formally will ask the National Highway Traffic Safety Administration to advise motorists to change their tires after six years, according to a top Ford scientist.
Ford also will recommend a tire aging specification based on oven aging and stepped-up load testing, said John M. Baldwin, polymer technical leader for the auto maker, who spoke at the 22nd Annual Clemson Tire Industry Conference at Hilton Head Island, held March 15-17. The company plans to release this specification by the end of March, combining oven aging and a 34-hour stepped-up load test. Such a requirement may reduce tire aging as a factor in tire failures, he said.
The extensive data Ford has generated-including analysis of peel results for age-sensitive tires as well as the results of the stepped-up load tests it devised-suggest strongly that six years is an appropriate and defensible limit for tire life, according to Baldwin. All the information has been there for tire manufacturers to see, he said, despite their claims otherwise.
"We take great umbrage at the accusations in news reports that we did not share our data," Baldwin said. Ford published five peer-reviewed articles on its tire aging research in various publications, he said, as well as presenting its results at industry meetings such as the Clemson Conference, ITEC and the ACS Rubber Division.
In addition, according to Baldwin, the F09 tire committee within ASTM International decided to honor Ford´s request for a task group on tire aging in 2003, the year after it initially rejected the suggestion. Initial task group results suggest that Ford and NHTSA were correct in positing that oven aging is the most appropriate way to accelerate the oxidative aging of tires for testing.
"We engaged the industry as soon as we started work on this," he said.
Ford worked with NHTSA on data collection for tire field aging, Baldwin said. The agency gathered tires from Phoenix-a city with a climate known to be tough on tires-while Ford gathered tires from Phoenix, Detroit, Los Angeles, Miami, Denver and Hartford, Conn. Oven aging and stepped-up load test results were normalized to Phoenix, he said.
Stepped-up load tests appear to sort out age-sensitive tire designs, Baldwin said. Of 15 different tires Ford tested, eight met or exceeded the performance criteria set for a six-year-old tire in Phoenix running under 34 hours of gradually increasing loads, he said.
But three of four light truck tires failed the requirement, he said, as did four P-metric tires. P-metrics probably could meet the six-year requirement with little or no modification, Baldwin said, but Ford is working with LT tire manufacturers to address tire aging issues. In the question-and-answer period, he said he suspected the inner liner as being the culprit in the LT tire failures.
Ford is not alone among auto makers in recommending a six-year service limit for tires, according to Baldwin. He said DaimlerChrysler A.G., BMW Inc., Toyota Motor Sales Inc. and Volkswagen A.G. (including both Volkswagen and Audi) also are recommending a six-year tire change in their owners´ manuals.
Although the Rubber Manufacturers Association dismisses chronological age as a criterion of tire service life, three of its members-Bridgestone/Firestone, Michelin and Continental Tire North America Inc.-are recommending 10-year service limits despite a total lack of data to support their claim, Baldwin said. A six-year advisory from NHTSA will help consumers avoid confusion, he added.
All of Ford´s tests were performed on original equipment tires, though replacement tires dominate the U.S. market, Baldwin said.
"But I wouldn´t say that replacement tires are so superior to OE tires that they can´t be lumped in with them," he said.
Ford has placed its five peer-reviewed articles in the NHTSA tire aging docket and soon will place other items there, including its petition to NHTSA and its presentations at the Clemson conference and elsewhere, Baldwin said.