P- Metric Tires

Most P-metric tires do not have exactly corresponding alpha/numeric tire sizes. A P235/70R15 is not equal in size and load capacity to an F78-15. Replacement tires should be of the same TPC specification number (size, load range, and construction) as those originally on the vehicle. If you must replace P-metric tires with other sizes, consult a tire dealer. Tire companies can recommend the closest match.

This is how you break down the code:

Caution: Do not mix different types of tires on the same vehicle such as radial, bias, and bias-belted tires except in emergencies because vehicle handling may be seriously affected and may result in loss of control and possible serious injury.

Tire Inflation

Check the tires monthly or before any extended trip. Set the tires to the specifications on the Tire Loading Information label. Install the valve caps or extensions on the valves. These keep out dust and water.

The kilopascal (kPa) is the metric term for tire inflation pressure. The tire pressure may be printed in both kilopascal (kPa) and psi. One psi equals 6.9 kPa.

Check the tire pressure under the following conditions:

When you inflate the tires to the recommended inflation pressures, the factory-installed wheels and tires are designed to handle loads to the tire's rated load capacity. Incorrect tire pressures, or under-inflated tires, can cause the following conditions:

Correct tire pressures, wheel alignment, and driving conditions affect tire life.

Heavy cornering, overly rapid acceleration, and heavy braking decrease tire life.

Replacement Tires

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

Replacement tires should be the same size, load range, and construction as the original tires. Replace the original tires with tires that have the same TPC specification number. Use of any other tire size or type may seriously affect the following items:

Important: Install new tires in pairs on the same axle. If you need to replace only one tire, this should be paired with the tire that has the most tread.

Replace tires when you find the following conditions:

1. The tires are worn to a point where 1.6 mm (1/16  in) or less tread remains, or, the cord or fabric shows. The tires may have built-in tread wear indicators that appear between the tread grooves when the tread is 1.6 mm (1/16 in) or less. When the indicators appear in two or more adjacent grooves at three spots around the tire, replace the tire.
2. The tread or sidewall is cracked, cut, or snagged deep enough to expose the cord or the fabric.
3. The tire has a bump, bulge, or a split. Slight sidewall indentations are normal and this should not affect ride.
4. The tire has a puncture, a cut, or other damage that cannot be repaired correctly because of the size or location of the damage.

All Season Tires

Most GM vehicles are now equipped with steel belted, all-season radial tires as standard equipment. These tires provide a soft, quiet ride, good handling, and long tread life. These tires provide all-season traction and low rolling resistance in order to help improve fuel economy. These tires have a 37 percent higher average for snow traction than non all-season radial tires previously used. Therefore these qualify as snow tires. You can identify these tires by an M+S molded in the tire sidewall after the size. The suffix MS also is molded in the sidewall after the TPC specification number.

Tire Chain Usage

When you use tire chains, most current GM vehicles require the following chain types:

These chains are specially designed to limit the "fly off" effect that occurs when the wheel rotates.

Manufacturers of tire chains have a specific chain size for each tire size. These ensure a proper fit when the chains are installed. Purchase the correct chains for the tires on which the chains will be used. Do not use rubber adjusters to take up slack in chains that are loose due to incorrect size. Always follow the chain manufacturer's installation instructions.

Use of chains may adversely affect handling. When using chains, remember the following steps:

Tire Loading Information Label

The tire information label is located permanently on the rear face of the driver's door. Refer to this label. This label lists the maximum vehicle load, the tire size (including the spare), and the cold inflation pressure (including the spare).

Wheels

Replace the wheels if the following exist:

Wheels with runout greater than specified may cause objectionable vibrations.