Tires do age over time and at some point need to be replaced by newer versions. The question is: When?
To date no one-including the tire makers themselves-has established a scientific answer, which is why the decision by Ford Motor Co. to offer a tire-age recommendation to its customers is premature and causing such consternation in the tire industry.
Let's give the auto maker the benefit of the doubt. It likely had customer safety and legal reasons in mind when it issued its new tire-aging guideline. It shouldn't be faulted for that.
But without having definitive data on which to base its recommendation, it has put tire manufacturers and tire retailers in a tough spot.
Ford's new position on tire aging, which it recently added to its Web site and owners' manuals, reads as follows:
``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. Heat caused by hot climates or frequent high loading conditions can accelerate the aging process. You should replace the spare tire when you replace the other road tires due to the aging of the spare tire.''
The tire in-dustry, however, insists that de-termining the age when a tire should be pulled from service is not so simple. It claims that other factors, such as how a tire is stored and maintained, have more to do with its degradation than does its chronological age.
This helps explain why no data exist definitively on this subject.
Ford's position raises myriad questions, such as, ``What is normal service for a tire?'' and ``When does the six-year life span start-from the date the tire was made or when it was put on the vehicle?''
Tire retailers, including Ford's own auto dealers, need answers to such questions. They are the ones on the front lines who must explain to customers what the six-year tire age limit is all about.
The National Highway Traffic Safety Administration is studying the effects of tire aging and hopes to add a tire-aging test to federal safety standards possibly as early as this summer.
Before other auto makers follow Ford's lead, they should wait until more information on tire aging is known. Already, DaimlerChrysler A.G. has said it plans to add the same advice to its owners' manuals in the 2006 model year.
Recent surveys have found the motoring public lax in maintaining their vehicles' tires. It's true that putting an age limit on tires may enhance the public's safety, but until someone can come up with definitive data about tire aging, it's best to hold off on establishing tire age limits.
Tire retailing is tough enough these days without having to debate customers about whether their 6- or 7-year-old tires are still good and safe.