These incidents illustrate not only the potential danger of buying used tires but also the perils of driving on aging tires — including those that have never spent a day on the road.

But for tires without that, a code of "328" could be from the 32nd week of 1988 — or 1978.

Clearly, these DOT numbers weren't designed with the consumer in mind.

Improper maintenance and heat accelerate the process.

Every tire that's on the road long enough will succumb to age.

Carmakers such as Nissan and Mercedes-Benz tell consumers to replace tires six years after their production date, regardless of tread life.

Tire manufacturers such as Continental and Michelin say a tire can last up to 10 years, provided you get annual tire inspections after the fifth year.But the rubber compounds in a tire deteriorate with time, regardless of the condition of the tread. For some people, old tires might never be an issue.If you drive a typical number of miles, somewhere around 12,000-15,000 miles annually, a tire's tread will wear out in three to four years, long before the rubber compound does.In February 2008, the owner of a 1998 Ford Explorer in Georgia needed a new tire for his SUV and ended up buying a used one.When he was driving two weeks later, the tread suddenly separated from the tire.They all mean something, but deciphering them can be a challenge. Tires with a three-digit code were made prior to 2000 and are trickier to decode.