A Tire Performance Criteria (TPC) specification number is molded in the sidewall, near the tire size on all of the original equipment tires. This specification number assures that the tire meets GM's performance standards for traction, endurance, dimensions, noise, handling, rolling resistance and others. Usually, a specific TPC number is assigned to each tire size.

Caution: Do not mix different types of tires on the same vehicle such as radial, bias, and bias-belted tires except in an emergency, because the vehicle handling may be seriously affected and may result in loss of control. This caution does not apply to the compact spare that is furnished with the vehicle.

Replacement tires should be of the same size, load range and construction as those originally on the vehicle. This can best be accomplished by using the tires of the same TPC specification number. The use of any other tire size or construction type may seriously affect the ride, the handling, the speedometer/odometer calibration, vehicle ground clearance and tire clearance to the body and chassis. This does not apply to the spare furnished with the vehicle.

Install new tires in pairs on the same axle. In order to equalize braking traction, if it is necessary to replace only one tire, the replacement tire should be paired with the tire that has the most tread.

Although they may appear different in tread design, tires built by different manufacturers with identical TPC specification numbers can be intermixed on the same vehicle.

Tires should be replaced when the following conditions are present:

1. The tires are worn to a point where 1.6 mm (0.063 in) or less tread remains, or the cord or fabric is showing. To help detect this condition, tires have built-in tread wear indicators that appear between the tread grooves when the tread is worn to 1.6 mm (0.063 in) or less. When the indicators appear in two or more adjacent grooves at three spots around the tire, the tire should be replaced.
2. The tread or sidewall is cracked, cut or snagged deeply enough to expose the cord or fabric.
3. The tire has a bump, bulge or split. Slight sidewall indentations are normal and should not affect the ride.
4. The tire has a puncture, cut or other damage that cannot be correctly repaired because of the size or location of the damage.