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.
People who live in warm weather and coastal states should keep this in mind when deciding whether they should retire a tire.
A tire that has not been mounted and is just sitting in a tire shop or your garage will age more slowly than one that has been put into service on a car. Conditions of use: This refers to how the tire is treated. Proper maintenance is the best thing a person can do to ensure a long tire life."If you take a rubber band that's been sitting around a long time and stretch it, you will start to see cracks in the rubber," says Kane, whose organization is involved in research, analysis and advocacy on safety matters for the public and clients including attorneys, engineering firms, supplier companies, media and government.That's essentially what happens to a tire that's put on a vehicle and driven. They may appear on the surface and inside the tire as well.Keep the visibility of the DOT number in mind the next time you are at a tire shop and the installer asks if you want the tires to be mounted with the raised lettering facing in.That potential inconvenience is going away, however.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.This cracking can eventually cause the steel belts in the tread to separate from the rest of the tire.An animation on the Safety Research & Strategies Web site shows how this happens.They were originally put on tires to make it easier for NHTSA to recall tires and keep track of their manufacturing date.To make matters worse, you might not always find the DOT number on the outer side of the tire.