Lack of proper maintenance and low air pressure are the two leading factors of premature tire wear. Inspect the tires yourself and check the inflation once a month, comparing it with the tire pressure recommendations labeled on your tire placard. The placard is usually located on the driver's side door jamb, or you can find the information in the owner's manual. Rotating your tires at recommended intervals will also help your tires last longer. Eventually, though, your tires will wear out. Knowing what to look for will help you determine when it's time to replace your tires.

Tread Wear

The tread of the tire is the part that touches the road and subsequently wears away. Friction created between the tire and the surface of the road creates heat that slowly erodes the tread. Once the tread wears down to a certain point, the tire should be replaced. Wear bars connect across the tread and are raised to a height of 2/32 of an inch. Once the tire tread meets the wear bars, the tires should most definitely be replaced. Keep in mind that a tire with even 4/32 of an inch will be compromised on snowy roads. The tread will not be able to pick up the snow and then disperse it fast enough.

Shoulder and Sidewall

Shoulder wear (the point where each inner and outer tread meets the sidewall) is usually caused by three leading symptoms. One is lack of tire rotation, especially for front tires that have to turn during steering. An underinflated tire will cave the center of the tread inward and ride on both the outer and inner shoulder. A toe alignment issue will create premature shoulder wear on tires. Incorrect toe angles will cause more wear on one shoulder than the other. Sidewalls are susceptible to dry rotting and cracking. Visible cracks can normally be seen along the lettering on the tires or around the bead. Tires with cracks that are longer than an inch in length, no matter the depth of the tread, should be considered for replacement.

Tire Maintenance

Check the tread depth of the tire in several locations along the circumference of the tire. Tires do not always wear evenly, especially if the vehicle is not following stringent rotation regimens. A penny or a depth gauge can be inserted into the tread to determine tread wear. Taking several readings along the circumference will show if the tire is wearing evenly or not. A penny should be placed upside down, showing Lincoln's head outward. If there is visible room between the top of Lincoln's head and the background of the penny, then the tread is less than 2/32 of an inch and should be replaced. Check the tire pressure once a month. Temperature fluctuations can wreak havoc with tire pressure. You should always check tires before they've been driven on and heated up. Use the tire pressure placard (or the owner's manual) to set the front and rear tires according to the recommended inflation. Tire inflation displayed on the sidewall of the tire is the maximum pressure that specific tire can take. Inflating to the maximum level leaves no room for increased pressure, which occurs when the tires heat up. Regular rotation regimens should be followed to achieve longevity of your tires. This places the front tires in the rear and the rear to the front, and some rotation procedures employ a crisscross pattern. Be sure the tires are not unidirectional (mounted in a specific forward direction) if you employ a crisscross pattern. Unidirectional tires can only be rotated front to rear axle without crisscrossing. Rotate your tires every 6,000 to 9,000 miles, or go by the maintenance schedule intervals in your owner's manual.

Source:

General Tire Information

Measuring Tread Depth With a Coin

Is it Time for New Tires?