Following the lead of its parent firm, Tokyo-based Bridgestone Corp., Bridgestone/Firestone (BFS) in America is recommending a 10-year service life for tires.
Bridgestone decided in September to follow a May 24 directive from the Japan Automobile Tyre Manufacturers Association (JATMA) that said motorists should be encouraged to have their tires inspected after five years of use and replaced after 10 years.
Nashville-based BFS, however, said there are no scientific or technical data to justify the 10-year guideline. It also said it endorses the call from the Rubber Manufacturers Association (RMA) for the National Highway Traffic Safety Administration (NHTSA) to generate tire aging data and issue a consumer advisory countering the idea that tires have a hard-and-fast expiration date.
Consumer group Safety Research & Strategies in Rehoboth, Mass., said BFS's announcement was a step in the right direction-but didn't go far enough.
``As time passes, the properties of the tires change,'' the JATMA directive stated. ``Since the environmental and storage conditions, as well as usage methods such as load, speed and air pressure, influence the change of rubber properties, inspection is necessary.''
At the same time, JATMA warned that the 10-year recommendation was only a guideline, not a rule. Some tires may remain serviceable after 10 years, while others may not last that long, depending on the above-named factors, it said.
In an October technical bulletin to its dealers, BFS said it too was adopting the JATMA recommendation.
``Although (BFS) is not aware of technical data that supports (sic) a specific tire service life, we believe it is appropriate to follow the JATMA recommendation in the interest of further encouraging consumers to focus on the importance of maintaining and properly replacing their tires,'' the tire maker said.
The idea that tires should be removed from service after a set period generally is anathema to U.S. tire makers. The RMA and the Tire Industry Association (TIA) reacted with dismay to the announcements by Ford Motor Co. and DaimlerChrysler A.G. this past spring that they would start recommending to their customers that they replace their tires after six years of use.
On June 10, the RMA wrote NHTSA asking the agency to issue a consumer advisory outlining the factors that affect a tire's service life. It also asked the agency to study the effects of aging on tires and generate data on aging. NHTSA has yet to answer the RMA.
However, Toyo Tire (U.S.A.) Corp. does not endorse the JATMA policy. ``We are watching all developments in this issue with great care, and we are in agreement with the RMA at this time,'' said Dave Taylor, Toyo vice president-technical.
NHTSA is working to develop an aging test to add to new tire safety standards, and the agency should issue a proposal on age testing sometime next year, an RMA spokesman said. The test will be geared toward age endurance, not expiration dates, he added.
``You need to have some scientific basis to establish any sort of tire service life, and that doesn't exist,'' he said.
Sean Kane, president of Safety Research & Strategies, said it was refreshing for a tire manufacturer to acknowledge that age degradation is a causal factor in tire failure. He also said BFS defaulted to Ford and DaimlerChrysler as to the time when tires should be replaced for age.
``It sets up a conflicting image,'' Mr. Kane said. ``But ultimately I think they'll advocate a six-year limit.''
Mr. Kane also said it was contradictory for BFS to continue to support the RMA's position.
``They're the best ones to tell us when their customers should replace their tires,'' he said. ``There's no one date, and we never said there was. But there are some guidelines. Do we expect every tire to last the same period of time? Of course not. But the onus is on the manufacturers to tell us what the guidelines are.''
Safety Research & Strategies has petitioned NHTSA for a six-year expiration date on tires and a requirement to place a non-coded date of manufacture on both sides of a tire. To date, the agency has answered neither petition.
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Motorists should be encouraged to have their tires inspected after five years of use and replaced after 10 years.