They’re possibly one of the most neglected systems on your car. We’re talking about your tires. After all, how often do most of us REALLY take a good look at those four round rubber things that keep our car on the road.
But here’s something to think about: The average “contact patch”, or the area of a car’s tire that at any one time is in solid contact with the road, is about the size of an adult’s hand. That’s right, the only thing keeping your car securely on the road are four tiny patches of rubber about the same size as four human hands.
That’s not a lot, so it’s important for the safety of you and your family that you make sure those contact patches are as effective as possible. With that in mind, we’ve come up with seven things you should do to keep your tires as healthy as possible:
1. Grab a Gauge
No other aspect of a car’s tire is quite as critical as proper inflation, yet it’s also one of the most commonly overlooked. While three-quarters of drivers wash their cars monthly, only one in seven correctly checks tire pressure with every flip of the calendar’s pages.
Under-inflated tires tend to sag in the middle, meaning the car is actually riding on a small contact patch located on either side of the tire. Over-inflated tires, on the other hand, ride on a small contact patch located in the very center of the tire. Either condition means that the tire’s “handhold” on the road is smaller than it should be, ultimately giving your car less grip on the road.
That’s why experts recommend checking your tires’ air pressure at least monthly. (If you don’t like getting your hands dirty, many auto service facilities will do this at no cost, and it usually only takes a minute or so.)
The air pressure inside a tire is measured in pounds per square inch (or psi), and it’s not uncommon for tires to lose one psi per month in common use. (Which is why some automakers are now filling tires with pure nitrogen, which tends to maintain pressure longer than compressed air, whose smaller oxygen molecules leak out over time.)
2. Check the Wear Patterns
Have you ever taken a close look at your tires? And not just the sides while you’re shining them up at the carwash. Examining the tread pattern on your tires can help identify problems long before they become dangerous.
For instance, if your tires are wearing more in the middle than at the edges, chances are the tires are over-inflated for the driving and loads you carry. Conversely, if they’re wearing at the edges more so than in the middle, chances are they tires are under-inflated (a much more common problem).
Also, you may notice that one edge of a tire is wearing more than the other. This could indicate an alignment problem (although some cars with “sport” suspensions are designed so that their tires ride on their inside edges, which increases cornering ability but also contributes to the tires wearing faster on their inside edges).
If you’re not sure you can identify a dangerous wear pattern yourself, ask your auto service technician to help.
3. Rotate Routinely
If you glance through the owners manual of just about any car on the road, you’ll find a factory-recommended interval for tire rotation, generally on the order of every 5,000-8,000 miles—or annually at the very least.
Tire rotation involves swapping the front and rear tires, along with crisscrossing the drive tires on most vehicles that do not use directional tires designed to spin in only one direction. This process is important because it ensures that the tire tread wears evenly, which maximizes tread life. Yep, if you rotate your tires, they’ll last longer and you won’t have to replace them as often. That makes the investment well worth it.
4. Achieve Balance
Ever heard your washing machine start vibrating like crazy? That’s because more clothes have collected on one side than the other, throwing the machine out of balance during the spin cycle. Get the washer out of balance enough, and it’ll literally walk across the floor.
Tires are the same way. When new tires are installed on a wheel, the tire/wheel combination is “balanced” using a machine that spins the pair and tells technicians where to install wheel weights (those tiny pieces of metal or plastic clamped to your wheels) to counterbalance any natural imbalance in the tire/wheel pairing.
As tires age, however, that careful balance can get thrown out of whack, meaning it’s a good idea to have your tires balanced at regular intervals. While hard-core experts recommend balancing tires every time they’re rotated, the consensus seems to be that tires should be balanced every second, third or fourth tire rotation, or if you begin to feel any unusual vibration or “shimmy” in the steering wheel.
5. Keep Everything Aligned
Your car comes from the factory with its suspension carefully aligned, meaning all four tires track straight and true in the same direction the car is travelling. (Or at least that’s how it’s supposed to work with new cars!)
But stuff happens. You back into a curb. You have a minor fender bender. You hit a pothole you didn’t see. All these things can knock the suspension out of alignment, causing the steering to vibrate and, more importantly, causing the tires to wear unevenly and in many cases excessively. So if your car’s steering doesn’t “feel” right, or if you notice unusual tire wear (like a “scalloped” pattern on the edge of the tires), your car’s suspension could need to be aligned.
6. Test the Tread
Ever heard of the “penny test.” It’s a quick and easy way to determine if your car’s tires have adequate tread life remaining. Simply grab a standard U.S. penny and turn it upside down so the top of Abe Lincoln’s head is toward the tire. Slip the penny between two of the tread blocks on your tires. If any of Abe’s head is covered up, it means you have at least 2/32nds of an inch of tread, which experts deem is the minimum necessary for safe driving.
But, if you can see all of Abe’s head, it’s time to have the tires replaced. Why? As tires wear, the tread blocks become shorter and shorter, meaning the channels between them—which are designed to shed water away from the tire in wet conditions—become shallower and shallower. This reduces the amount of water that can be channeled away, potentially increasing the odds that your car could hydroplane on wet roads and skid out of control. Not a pretty picture.
If it is time to replace your tires, experts recommend replacing them in pairs (for instance, if the rear tires are more worn than the fronts, you might just replace the rear tires) or in sets of four. Replacing just one tire makes your car ride unevenly, which could affect how the car steers and stops.
7. Don’t Forget the Spare
It’s the one item on our cars we often forget until we need it the most—the spare tire. While you won’t have to worry about tread wear issues with the spare, when it comes time to checking the inflation pressure, it’s a good idea to routinely check the spare tire, as well. After all, how frustrating would it be to have to change a flat tire only to find out the spare is flat, too!
The four little handprints your tires make on the road can mean the difference between driving securely or losing traction and possibly having an accident. Help your car’s tires live up to their purpose as best they can by following these tips and showing them a little TLC—“tire” loving care!
Editor’s note: For a neat interactive demonstration of the important of correct tire pressure and maintenance, visit: www.safercar.gov