There's no longer any debate. Tires older than six years should be discarded and replaced, even if they otherwise appear to be in good condition with plenty of tread. In fact, they should be tossed out even if they've never been used. That's because tires older than six years are prone to "detreading." Detreading is a type of tire failure where the tread peels from the tire much like the skin may peel from a banana.
Detreadings are more dangerous than flats or blow-outs. Some vehicles, including SUV's, can become uncontrollable after a detreading and can roll over, especially if it's a rear tire that fails.
One need look no further than the vehicle's owner's manual for guidance. Almost all the car manufacturers now warn to replace tires after six years, regardless of condition. That includes Volvo, Nissan, Toyota, BMW, and even Ford. In fact, Ford posted a warning on its website:
Tires degrade over time, even when they are not being used. It is recommended that tires generally be replaced after 6 years of normal service. Heat caused by hot climates or frequent high loading conditions can accelerate the aging process.
Until recently, the tire manufacturers argued that tires were good for at least 10 years. Maybe even indefinitely if they had adequate tread. It's only now that the tire makers agree that the "six-year" rule should be followed.
What gives? Wouldn't a tire manufacturer want consumers to toss out tires sooner, so that they could sell more?
Tire manufacturers make tires in batches and then store them until needed. That' means the tire you buy at a tire store as "new" may be up to 10 years old. Sometimes even older. If buyers began rejecting those tires, tire manufacturers would have to change their whole way of making and distributing their product to get them to market and sold while still "fresh."
Consumer groups have argued that tire makers should stamp the year of manufacturer on the outside tire sidewall, so the consumer would have no trouble telling how old the tire is. Or at the very least, tire shops should be required to advise customers when the new tire they are buying isn't exactly "new."
Tire makers and tire shops resist. They say the code containing the tire's date of manufacture is stamped on the inside sidewall for anyone to see. But the problem with that is the coded information is hard to find and is, well, in code.