Your tires are your car's only connection to the road. They're overlooked as safety items, but sometimes they're the first place where a problem will appear. We show you how to read your tires and know what the warning signs mean.
It Looks Like: Your tire is worn down only in the middle.
The Diagnosis: This tire was overinflated, causing the center ring only to contact the road. Consequently, whoever drove this car had only a fraction of the rubber contacting the asphalt, so his or her traction suffered.
To find the correct tire pressure, check the door placard or the owner's manual. Check the pressure when the tires are cold, before you start driving. Some people claim that you should overinflate tires to reduce rolling resistance and increase fuel economy. But that's a fool's game. You might save some fuel, but you'll pay more in prematurely worn tires.
If your pressure is correct but you still see center wear, this could indicate that the wheel and tires are not properly matched. There is one caveat here: Woody Rogers, product information specialist at Tire Rack, says that some rear-wheel-drive vehicles can produce center wear on certain tires, even if they're properly aired up and maintained. But that's true only for high-powered sports cars.
It Looks Like: Pretty self-explanatory.
The Diagnosis: This usually comes from hitting a pothole, curb, or debris. Underinflation and overinflation put tires at a greater risk of damage from impacts.
Large cracks in the sidewall that runs along the rim are either impact-related or caused by chronic underinflation. Numerous small cracks in the sidewall or tread blocks come from exposure to the elements and age.
It Looks Like: A pattern of alternating hills and valleys
The Diagnosis: It happens when worn or damaged suspension components cause the tire to bounce as it travels, coming down harder on some spots of the tire than others. Bad shock absorbers are the usual cause, though anything that connects the wheel to the rest of the car could be a culprit.
Be careful with your diagnosis, though. Even tire shops sometimes incorrectly identify feathering or heel-toe wear as cupping. A wheel that is out of balance may also cause cupping or bald spots to form, though there will be fewer hills and valleys than you'd see with cupping caused by a failed shock absorber.
It Looks Like: Cupping or scuffing, but in a diagonal pattern.
The Diagnosis: This tire trouble is most often seen on the rear tires of a front-wheel-drive car with an incorrect toe setting. Insufficient tire rotation intervals may also cause a diagonal swipe. A third possibility: If you frequently carry heavy loads in the trunk or cargo area of a vehicle, that may change the geometry of the suspension, leading to a diagonal swipe.
It Looks Like: The inside and outside edges are worn down; the middle is not.
The Diagnosis: his is a telltale sign of underinflation. Too little pressure is arguably the most dangerous condition for a tire, as it will flex more and the heat that builds up could cause a blowout. (Remember the Ford Explorer Firestone mess? The cause was mainly underinflated tires.) And an underinflated tire won't absorb bumps well and may knock the front end out of alignment or damage the suspension.
How to Avoid Underinflation: Again, keep an eye on your tire pressure by checking it monthly. Don't rely on the car's tire-pressure monitoring system to let you know when a tire is low on air. "[The warning system's] threshold is typically 25 percent underinflated," Rogers says. This means a tire that should be at 28 psi could be down 22 psi before you see a warning light. And that could be low enough for you to destroy a tire.