Tire service begins with a visual inspection of your tires for abnormal tread wear or other damage. Check your air pressure weekly with a pencil-type gauge for consistent readings. Service station gauges may not be accurate.
Visually inspect your tires for:
Bias ply tire will show different wear patterns if they are run over or under inflated. A bias ply tire operated while under inflated will show greater wear on the outside edges of the tire tread. A bias ply tire that is overinflated will show more tread wear in the center.
Individual radial tires set their own wear patterns. The only way to check for proper inflation in radial tires is the weekly pencil gauge check.
Improper tire inflation affects steering, braking, tire wear, and is a major contributor to high fuel consumption. All tire manufacturers recommend maximum inflation pressures for their tires. These are listed on the sidewall of the tire. Pressures should be measured when the tires are cold. This means the tires should have been standing for at least three hours or driven less than one mile after standing for three hours.
If you need to add air to your tires while on the road, equalize the pressure in the tires on each axle. Otherwise, the uneven pressures will cause erratic steering.
According to the Department of Energy, most vehicles can improve fuel mileage by two percent by keeping all tires at maximum pressure all the time. This may, however, give our vehicle a harsher ride. Check your tire pressure with a pencil-type gauge at least twice a month, including your spare tire. Invest in your own gauge to be sure you can check tires when they are cold.
Out-of-alignment tires will show uneven tread wear on the outside edges, on the inside edges, or a unique feather-edged or scuffed wear pattern. If you notice any of these patterns, check with your wheel alignment specialist.
All car tires made since August 1968 have tread wear indicators which appear as continuous bars across the entire tread. These bars are placed at even intervals in the tire tread, but are only visible when the tread has worn down to the last sixteenth of an inch. Replace the tire when these wear indicators are exposed in two or more adjacent grooves on the tire.