WASHINGTON—Ford Motor Co. has started recommending tires be replaced after six years of normal use, claiming they degrade over time, and DaimlerChrysler A.G. is about to do the same.
Tire industry representatives, who insist there are too many variables in tire aging to set a hard-and-fast expiration date, are in an uproar over the auto makers´ decision.
On its Web site and in its owner manuals, Ford now states: "Tires degrade over time, even when they are not being used. It is recommended that tires generally be replaced after six years of normal service."
DaimlerChrysler will add the same advice to its owners´ manuals beginning with the 2006 model year, a company spokeswoman said. She said DaimlerChrysler decided to take that action after discussing the issue with a number of tire manufacturers, which she declined to name.
The Rubber Manufacturers Association would like to know what tire makers she´s talking about. An RMA spokesman said no tire maker would have told DaimlerChrysler a six-year recommendation is a good idea.
"I can´t imagine that happening," the RMA spokesman said. "It doesn´t make any sense. Ford has never shared any (tire-aging) data with us that we know of, and the same with DaimlerChrysler."
The tire industry maintains storage and maintenance have more to do with a tire´s degradation than chronological age.
A Ford spokesman said the company based its decision on its ongoing research in tire aging. John M. Baldwin, the Ford polymer science technical specialist who heads the company´s tire-aging research, could not be reached for comment. In a speech he gave at the Clemson University Tire Industry Conference in March 2004, Baldwin said aging is a crucial element in tire degradation.
This fact became apparent in Ford´s study of the Firestone Wilderness AT tires, recalled in August 2000, that were standard equipment on Ford Explorers and other Ford sport-utility vehicles, Baldwin said at the conference.
"If you look at the first two years of service for those tires, there essentially were no reports of failure," he said. "It took two years for something to happen. Then, when you look at two vs. four years of service, peel strength had dropped 50 to 75 percent in the field. Obviously, the rubber´s changing."
A General Motors Corp. spokesman said his company makes no specific recommendations as to tire age but advises vehicle owners to care for their tires properly.
The National Highway Traffic Safety Administration is studying the effects of tire aging, and hopes to add a tire-aging test to federal tire safety standards perhaps as early as this summer.
The industry beat back an effort early in 2004 by Sen. Mike DeWine, R-Ohio, to include a tire expiration date provision in a larger motor safety bill. A measure to require tire manufacturers to mold non-code dates of manufacture on both sidewalls was introduced this year in the New York legislature.
A proponent of expiration dates on tires is encouraged by Ford and DaimlerChrysler´s decisions.
"Ford´s announcement carries a tremendous amount of weight, considering the work they´ve done already in studying the effects of tire aging," said Sean Kane, president of safety activist group Safety Research & Strategies Inc. "This will have an effect not just among vehicle manufacturers, but also within the tire industry and at NHTSA, which is following Ford´s lead in tire-aging research."
For two years he has tried to get NHTSA to establish expiration dates for tires. He plans to send new information to the agency, claiming tires at least six years old have been responsible for 70 highway accidents that caused 52 deaths and more than 50 serious injuries.
The tire-aging claims don´t wash with Tom Cadotte, vice president of marketing for Flynn´s Tire Co., a Mercer, Pa.-based tire store chain with 17 outlets in Pennsylvania and Ohio.
"I would rather have a properly stored 6-year-old tire than an improperly stored 1-year-old tire," said Cadotte,
A one-time Kelly-Springfield Tire Co. vice president of marketing for consumer products, Cadotte said bad press about tire aging could cause big trouble for tire retailers.
"After one of those news stories, if you show customers a tire that´s been stored four or five years, they´ll throw up their hands and say, ´Oh no, that´s too old! I don´t want that!´ " he said.