Probably the biggest thing most people ignore about their tires is inflation; underinflation can take thousands of miles off a tire's life.

Tire inflation should be checked a minimum of twice a month. And if air is needed each time, then checks should be made more often. Tires should be inflated to the pressures indicated in the car-owner's manual.

But other aspects are important too -- wheel balancing and wheel alignment. When should wheels be balanced and aligned? WHEEL BALANCING -- Tires, when you think about it, are amazingly durable. They go thousands of miles, through all kinds of weather, supporting the weight of the car and its occupants, making quick stops, hitting pot holes, and so on.

Stillm, they're not quite perfect: Almost every tire has a slight imbalance in it, some spot that's a little heavier than a corresponding section elsewhere on the tire.

This isn't because tire makers are careless or incompetent; it would be prohibitively expensive to build a perfectly balanced tire, and there's no need -- wheel-balancing gets rid of the imbalance in the tire.

There are three kinds of wheel balancing -- static balancing, dynamic (computer) balancing, and on-car balancing.

Static balancing, also sometimes referred to as bubble balancing, is the cheapest method of balancing. And for most tire-wheel combinations it works adequately.

Spin-balancing is more expensive. But it is a better method. The wheel (tire mounted on the rim) is placed on a computerized machine that spins it; balances the tire in two different planes, whereas static balancing deals with only one plane.

On-car balancing is done generally on older cars that are having problems getting their wheels balanced in the static or dynamic balancing modes. With this type of balancing, the wheel is not removed from the car. A special machine turns the wheel while it is still mounted on the car. This procedure results in balancing not only the tire and rim, but the rest of the rotating mass (roter, brake drum, etc) as well.

One important thing to remember about on-car balancing -- when a wheel is removed from the car, the balance is lost, unless the wheel is put back on the car in exactly the same position as it was when it was removed.

To be sure you get it back on in the right position, before removing the wheel, make a chalk mark on the end of one stud, and make a corresponding chalk mark on the rim by the hole for that stud. When you put the wheel back on, be sure the chalk marks line up -- that way you know the wheel went back on in the same position.

Regardless of which method is used, wheel weights of various size are used to put the wheel in balance. WHEEL ALIGNMENT -- As long as your car handles all right, and tires are wearing evenly there's no reason to check alignment.

Sometimes a handling problem, such as the car's pulling to one side, is attributed to wheel misalignment, when really the only problem is that one of the tires is low.

But if the tires are properly inflated and handling is strange, or tire wear is uneven, have the car checked out. You yourself can inspect the tires for wear.

Excessive wear at both outer edges of a tire but little or no wear in the center probably indicates under-inflation. Excessive wear in the middle of the tread but little wear on the outside edge likely means over-inflation.

Wear on only one side of a tire probably means excessive camber, which is a wheel-alignment problem.

If the edges of a tire tread are feathered, this probably meand incorrect toe-in, which is another wheel-alignment problem. With this type of wear, if you rub your fingers across the tread in one direction the edges of the tread will be rubbed smooth, and will feel relatively smooth to your fingers.

Rubbing in the other direction, however, the treads will feel sharper because they're a little higher, this is called feathered wear.

Bald spots probably indicate that the wheel is unbalanced.