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Like many other consumer goods, tires are designed to last much, much longer than they did at one time. In the 70s, before radial tires were commonplace, bias-ply tires would typically come with a 20,000 mile treadwear warranty, barely long enough for two years’ worth of service for most drivers. In the 80s, the radial designs available then might last 40,000 miles; today, a 60,000 mile treadwear warranty isn’t uncommon, even with low-priced tires. Treadwear by itself, however, doesn’t tell the entire story.

A tire uses a complex rubber compound composed of natural rubber, various synthetic rubber formulations, carbon black, silica and other elements, which are then molded and bonded to layers of fabric and steel cords. That structure has to retain air under pressure and support a few thousand pounds’ worth of a vehicle’s weight. It’s then exposed to the sun’s ultraviolet rays, ozone, heat and other factors. Taking all that into account, the U.S. National Highway Traffic Safety Administration and various industry groups have now stated that tires that are 6 to 10 years old should be replaced, regardless of how many miles they have on them.

Age and weathering can crack and dry out tires, no matter what sort of care they have been given. That means that if you’re driving an older car, the spare tire might be compromised even if it’s never been on the ground. It also means that Grandma’s ’92 model Buick with only 45,000 miles probably needs tires, if they’ve not been replaced before.

European manufacturers have called for a six-year cycle on tires, although that takes into account the wide-open speeds of the Autobahn and Italy’s Autostrada. Still, Chrysler, Ford and General Motors have followed their lead and recommended that their OEM tires be replaced after six years.

Reading the Date Code

The good news is that every tire carries a date code that’s included in the information stamped on the tire sidewall. This can be a little confusing for most people, since tire sidewalls are embossed with a lot of numbers and other somewhat-esoteric information. You’ll find a DOT code, though, with “DOT” as its prefix. The DOT code is usually long and contains a lot of letters and numbers, but there are four digits at the end that denote week and year of manufacture. This could be a typical DOT code:

DOT U2LL LMLR3511 

In this instance, the tire was made on the 35^th week of 2011.

Bear in mind that a tire’s service life also includes the amount of time it spent in storage or at a distribution center. The sell-by date of tires may not be as crucial as it is for something like milk or eggs, but it’s important to bear in mind anyway. So what does this mean for you as a driver?

Tire maintenance is still the most crucial factor in getting the most miles out of your set of tires. You should rotate your tires at regular intervals and check them for treadwear, uneven wear patterns and other signs of damage. While you’re at it, though, get a close look at the sidewalls and look for cracking or signs of dry rot…and hang onto your receipts from when you bought them.

Got any questions about aging tires? Or is it time for a tire rotation, or maybe just a whole new set of tires? Give us a call at Star City Tire & Battery Service at 6802 Peters Creek Road in Roanoke and make an appointment!