Chances are, there's some source less bit of knowledge rattling around in your head. You don't know how it got there or where it came from, but you believe it. Maybe your convictions on tire life falls into that category. We've always held that that our favorite round rubber bits had a use life of about two years before age had a serious negative impact on performance. Turns out, we were wrong. Way wrong.
Woody Rodgers, a tire product information specialist, has been with Tire Rack for sixteen years, and he says that given proper storage and care, tires can last you up to a decade.
"I won't say a tire has the shelf life of gravel," Rodgers said, "but it's close to that."
When properly stored in a climate controlled warehouse, tires have an almost unlimited shelf life, and once they're on the road, proper care can add many years to a tire's life.
"In general, we see six years of service with no more than 10 years of total life since manufacture."
Rodgers calls this the 6 or 10 rule, and those two numbers are important. In this case, service is any time the tire is on the vehicle, in use, or stored outside. Exposure to ozone or UV rays shortens that lifespan, as do wide swings in temperature.
Of course, that all depends on where you live and how you drive.
"The reality is, service life can vary so much from one driver to another and one part of the country to another, that it's really difficult to say that it's X [years]," Rodgers said.
Instead of marking a date on your calendar, Rodgers recommends inspecting and maintaining your tires every month. Keep an eye out for cracks in the sidewall caused by either sun exposure or under inflation, and monitor your tread depth. Most of us rely on the wear bars on the tires themselves, or the ancient penny test to tell us when it's time to swap shoes, but Rodgers says that's a problem.
Wear bars usually present themselves at 2/32 tread depth, which is fine for dry climates like Los Angeles or Phoenix, but not so great for parts of the country that see regular rain. Instead, 4/32 of tread depth is the minimum safe threshold for evacuating water from beneath the tire and reducing the chance of hydroplaning. How do you measure 4/32 without a depth gauge? Rodgers says if you can stick a quarter in the tread and not see the top of Washington's head, you're in good shape. If you can, it's time for new rubber.
Likewise, snow and all-season tires require even more depth to effectively evacuate snow and slush: about 6/32.
Then there's inflation. Rodgers says tires naturally loose about 1 psi per month on average, and lose or gain 1 psi for every 10 degree drop or increase in ambient temperature. Those changes require regular monitoring and adjustment, and your vehicle's tire pressure monitoring system may not be up to the task.
Most systems are calibrated to alert the driver about a low tire only after the pressure has dropped below 75 percent of the recommended figure. Rodgers says that's well past the point of damaging the tire and shortening its life, to say nothing of sucking down your fuel economy. For the best reading, check your tire pressures with a good gauge in the cool ambient air of the morning – not in your garage.
And what about storage? Rodgers says that for most street tires, it doesn't matter whether they're stacked on the sidewall or stood up on their tread, mounted or unmounted. As long as your tires are out of sunlight, away from ozone, and in an environment with a stable temperature, you're good to go.