How can I make my tires last longer?

When's the last time you checked the air pressure in your tires? If you're like most people, it's been a while. And like most people, your tires are probably under-inflated, too.

Once a month, check the air pressure with a tire pressure gauge when the tires are cold. It's best to do it in the morning before the car's been driven anywhere at all or at least a few hours after its last trip. Even a couple miles on the road can warm up the air inside the tire, causing it to expand and giving you an inaccurate reading. Warm summer days will expand the air inside the tires, too. A cold reading will give an accurate measure of pressure and, once filled, leave room for expansion while you're driving.

If once a month seems excessive, keep in mind that tires can lose one or two pounds of pressure a month. Neglecting this chore for six months means there's probably a little flat spot on the bottom of the tire where it meets the road. Having more tire in contact with the road means more surface area to wear out -- not to mention the fact that it can negatively affect your gas mileage, too.

Newer cars equipped with tire pressure monitoring systems (TPMS) lend a hand in the air pressure department. The basic systems alert the driver when a tire is low and going flat with an exclamation point inside a tire symbol on the dashboard. Other more sophisticated systems offer the tire pressure readings for each tire -- no pressure gauge required.

Once your tires are properly inflated, they should be properly aligned. On the next page, let's see how that can affect tire longevity.

When you take your car to the tire shop these days, they check your alignment with laser beams and other sci-fi-worthy instruments. This is great for absolute precision, but if you're trying to determine if you've got an alignment problem in the first place, there are a couple ways to check for yourself -- right in your own driveway.

Check for camber, the tilt of the tire toward or away from the frame of the car, by standing in front of the parked car (or behind it, if you're checking the rear tires). If the tires tip in -- that is, the tops are closer together than the bottoms -- the tread will wear away on the inside of the tire first. If they tip out -- bottoms closer than the tops -- there will be more wear on the outside.

It's also pretty easy to check the toe, or stance of the tires, in the driveway. Think of the tires on one axle, either front or rear, as feet. The fronts of the tires in either case are where the toes would be. Toe in means the fronts of the tires are closer together, like standing pigeon-toed, and the tread will wear from the outside. Toe out means the rear of the tires are closer together, like first position in ballet, and the tires will wear from the inside. The wear from toe-out tires is sometimes called "feathering."

If you notice your tires are slightly off angle or if you see the tell-tale tread wear, it's time to get your tires aligned to increase their usefulness. While you're at it, you might want to get those tires rotated, too, which we'll discuss next.

This probably goes without saying, but it's always worth reminding car owners that rotating the tires means they'll wear more evenly. And even wear is the key to getting the most out of a set of tires -- no matter what type of tire you're using.

Rotating the tires means taking them all off and moving each one to a new position on the car. Rear tires wear differently than front tires, depending on whether it's a front-wheel-drive or rear-wheel-drive car. Left tires wear differently than right ones, too, depending on the number of turns taken in either direction or how carefully you parallel park. We've probably all scraped a right tire or two in our time; rotating the tires means not scraping the same poor tire over and over again against the curb.

Most automakers and tire manufacturers recommend rotating the rubber every 6,000 to 8,000 miles (9,656 to 12,875 kilometers). If your car has a full-sized spare -- a tire that looks just like the ones mounted on the car and not a little black donut for emergency use -- then make sure that the fifth tire is included in the rotation, too. That will help reduce wear on each tire quite a bit and give you the maximum life for your set of tires.

When you're talking about tires, a little maintenance goes a long way. We're hoping that if you follow these tips, your tires will go a long way, too. For more information about tires and other related topics, follow the links on the next page.