Tires tend to lose air over time. Buy a digital tire gauge and check your tires once a month and before a long trip. Proper inflation pressures can be found in your owner's manual or on a sticker on the car (usually on the driver's doorjamb or fuel-filler lid.)

Remember to check tire pressure only after the car has been sitting for several hours in order to ensure that the tires are cold -- the friction of driving heats the tires and increases pressure, which can sometimes hide an under-inflated tire.

SPARE TIME.
Getting a flat tire and discovering that your spare is flat too is a miserable experience. Inspect your spare as you would your other tires. If you have a compact spare, the inflation pressure will usually be written on the tire.

IN DEPTH.
The tire tread provides the gripping action and traction that prevent your vehicle from slipping or sliding, especially when the road is wet or icy. In general, tires are not safe and should be replaced when the tread is worn down to 1/16 of an inch.

An easy way to check your tread depth is to place the edge of a penny upside-down into the grooves of the tire's tread so that you can see President Lincoln. If you can see all of Lincoln's head, it's time for a new set of tires. If some of his head is hidden inside the treads of your tires, you still have some time. Also, rotating your tires every 5,000 to 7,000 miles will help ensure that all four tires wear at the same rate.

IT'S ALL IN THE ROTATION.
Rotating your tires from front to back and from side to side can often reduce irregular wear. Look in your owner's manual for information on how frequently the tires on your vehicle should be rotated and the best pattern for rotation.

WHAT NOT TO WEAR.
When you check tread depth, check both the inside and outside edge of the tires. Uneven tire wear is usually a sign that your car is out of alignment. Proper alignment optimizes handling and helps prevent premature tire wear.

STAY BALANCED.
To avoid vibration or shaking of the vehicle when a tire rotates, the tire must be properly balanced. This balance is achieved by positioning weights on the wheel to counterbalance heavy spots on the wheel-and-tire assembly. A wheel alignment adjusts the angles of the wheels so that they are positioned correctly relative to the vehicle's frame.

This adjustment maximizes the life of your tires and prevents your car from veering to the right or left when driving on a straight, level road. These adjustments require special equipment and should be performed by a qualified technician.