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Everyone who drives in the Snow Belt is well-aware that we are in the middle of pothole season. Water is freezing, melting, freezing again and making hundreds of mini grand canyons in our roads. And as hard as you may try, avoiding all of them, all of the time, is near impossible. Tires are the first line of defense against these craters, they take a lot of punishment -- even on sunbelt roads -- so it’s good to know the signs your tires had enough. And that goes way beyond whether they continue to hold air.

“Back in the '50s, when you traveled, you took two spare tires with you because tires blew out all the time,” explains Woody Rogers, Tirerack’s director of tire information. “Nowadays, tires can withstand amazing bumps and bangs. By the time (the problem) shows itself as a crack or a bulge or a small vibration, it could be days, weeks, months after you hit that pothole.” Rogers knows tires inside and out and wants to share the different warning signs that your tire's health is failing.

When you smack a pothole, your tire's sidewall (the part between the tread and the wheel) starts to fold. Hit it hard enough and your car’s rubber folds over completely, especially if the wheel bends at all. “The wheel can’t bend if the sidewall doesn’t get compressed all the way, folded over," Rogers said. "It can’t because the rubber cannot exert enough force to bend the wheel. Some sidewalls may endure that; most probably not. If you have a bent wheel, you want to take a really close look at the tire. Because it probably has a stress point that increases the chances of failure in the future.” Remember, even if the wheel didn’t bend, the tire could be irrecoverably damaged.

A tire’s sidewall is effectively another spring on the car; fully compressing it is bending and straining rubber, and the structure inside, beyond what it’s designed to withstand. Rogers wants you to think of it this way: “It’s like getting punched in the face by a boxer -- why does the cheek skin of a boxer split open? It’s squished so hard between the boxing mitt and the cheekbone, it tears. The sidewall of a tire does the same thing, it tears. It can be all the way through or part of the way through and you see a crack in the rubber; you’ll often see the ends of brown dots embedded inside the crack -- those are the individual strands of the body core fabric that have been cut, and that’s your safety net and you now cut the safety net.”

If the outside sidewall looks fine, but the wheel did bend and something doesn’t feel right, Rogers wants you to check something else. “Go to the tire store and what you can do is find the bend in the wheel; they should mark the tire and carefully dismount the tire and look at the inner liner. It’s a lot like the canary in the coal mine -- it’s sensitive. It will show a witness mark, as a smudge usually, where the impact took place. It’s been pinched enough to make a smudge or a crack or a line or some other obvious localized spot in the sidewall area, then you’ve got some damage. You can’t see it, it’s inside, but it’s damaged and you should replace the tire.”

Dire stuff. Fortunately, here are a few preventative measures. First, think twice before getting the biggest wheels and lowest profile tires. The taller the sidewall, the more cushion before wheel meets pavement and that gives the shock absorbers more time to react too. Also, check your tire pressure. Rogers explains it this way: “If a tire was driven on while low on air, that shows in a certain way … If a tire never experiences stress beyond what it’s designed for, after 60,000 miles, the inner liner will look pristine. It doesn’t get cracked or worn out or whatever. But any kind of sustained underinflation or impact damage, you’ll see it on the inner liner.”

Much more than a simple puncture, pothole damage can take many forms. To prevent your tires from failing in the future, it’s good to know the signs of stress. And keep those tires properly inflated!