Lift each corner of the vehicle (one corner at a time) with the floor jack and place a jack stand beneath the vehicle to support it. This will allow you to inspect the circumference of the tire to determine tire wear.
Place the vehicle in neutral gear to inspect the drive axle. Apply the parking brake for a front-wheel drive vehicle while checking the front tires. Release the parking brake and place in gear or park (except rear-wheel drive vehicles) when inspecting the rear tires.
Check the outside edges of the tire. If both edges of the tire are worn more than the center tread, then the tire is under-inflated. This is because the center tread collapses and the tire rides on the edges. If the center tread of the tire is worn more than the outside edges, the tire is over-inflated. Over-inflation causes the tire to ride on the center of the tire and pulls the edges of the tire away from the road. Check and adjust the tire pressure (using an air compressor to fill or pressing the valve core to release). Locate the tire information label on the driver's side door jamb to learn what the manufacturer recommends for air pressure in the front and rear tires.
Determine if the tread wear on the front tires is present on one edge, but not on the other. This could be the result of a poor rotation regimen; loose or broken front-end component(s); or the vehicle may be out of alignment. Front tires handle the steering motion of a vehicle so, as a result, it is common for the edges to wear more quickly than the rear tires.
Inspect the tread and sidewall for any foreign objects such as nails or screws. Any time you have to put air in a tire, recheck the air pressure regularly for a few days to make sure it is maintaining the pressure.
Determine if the tread wear has uneven bald spots, is cupped, scalloped or saw-toothed. These types of uneven wear would indicate a poor wheel balance and rotate regimen, a bad alignment or weak suspension components.
Measure the tread depth of each tire with a a quarter and a penny (see References). The edge of a penny to the very top of Lincoln's head is 1/16 of an inch. A tire is considered expired with this minimal amount of tread left. The edge of a quarter to the very top of Washington's head is 1/8 of an inch. Although this is acceptable tread life for a tire, the tire will not handle braking or bad weather conditions as well and should be considered for replacement soon.Tires are expensive to replace and there are many variables that can cause premature wear. Rotating and balancing regularly will ensure the tires last as long as possible. Checking regularly for proper inflation and uneven wear will also help prevent flats and help you discover potential problems before they become too serious.