Tires: Description and Operation

Tire Chain Usage
Due to limited tire-to-body clearance on certain vehicles, recommendations for tire chain use are published in the Owner's Manual. When tire chains need to be used, most current General Motors vehicles require SAE Class S tire chains. These may also be designated as 1100 Series, type PL tire chains. These chains are specifically designed to limit the fly off effect which occurs when the wheel rotates.

Be sure that only fine-link chains are used which do not add more than 15 mm (0.59 inch), including the lock, to the tread surface and the inner sides of the tires.

Manufacturers of tire chains have a specific chain size for each tire size to ensure a proper fit when the chain is installed. Be sure to purchase the correct chains for the tires on which they are to be used. Use rubber adjusters to take up any slack or clearance in loose chains.
Use of chains may adversely affect vehicle handling.
When tire chains are installed, follow these precautions:
^ Adjust speed to road conditions.
^ Avoid sharp turns.
^ Avoid locked-wheel braking.
To prevent chain damage to the vehicle, install the chains on the front tires as tightly as possible. Tighten them again after driving 0.4-0.8 km (0.3-0.5 mi). The use of chains on the rear tires is not recommended because they may contact the vehicle and possibly damage it. If chains must be used on the rear tires, be sure there is sufficient clearance between the chains and the body. Do not exceed 70 km/h (45 mph) or the chain manufacturer's speed limit, if lower. Avoid large bumps, potholes, severe turns, and any other maneuvers which could cause the tires to bounce. Follow any other instructions of the chain manufacturer which do not disagree with the above instructions.

Tire Inflation Description
The pressure recommended for any vehicle line is carefully calculated to give a satisfactory ride, handling, tread life, and load-carrying capacity.

Tire pressure should be checked monthly or before any extended trip. Check the tires when they are cold, after the vehicle has sat for 3 hours or more or has been driven less than 1 mile. Set the tire pressure to the specifications on the tire label located on the rear face of the driver's door. Tire inflation pressure is also given under Tire and Wheel Specifications .

Valve caps or extensions should be on the valves to keep dust and water out.

For sustained driving at speeds up to 140 km/h (85 mph), inflate the tires to the pressure recommended on the tire. Sustained driving at speeds faster than 140 km/h (85 mph), even if permitted by law, is not advised unless the vehicle has special high-speed tires available from many tire dealers. Tire pressures may increase as much as 41 kPa (6 psi) when the tires are hot.
Higher than recommended tire pressure can cause:
^ Hard ride
^ Tire bruising or damage
^ Rapid tread wear at the center of the tire
Lower than recommended pressure can cause:
^ Tire squeal on turns
^ Hard steering
^ Rapid and uneven wear on the edges of the tread
^ Tire rim bruises and rupture
^ Tire cord breakage
^ High tire temperatures
Unequal tire pressures on same axle can cause:
^ Uneven braking
^ Steering lead
^ Reduced handling
^ Swerve on acceleration
^ Torque steer

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

Caution: Mixing tires could cause you to lose control while driving. If you mix tires of different sizes (other than those originally installed on your vehicle) or types (radial and bias-belted tires), the vehicle may not handle properly, and you could have a crash. Using tires of different sizes (other than those originally installed on your vehicle) may also cause damage to your vehicle. Be sure to use the correct size and type tires on all four wheels.

Use only replacement tires with the same size, load range, and construction as the original. The use of any other tire size or construction type may seriously affect ride, handling, speedometer/odometer calibration, vehicle ground clearance, and tire clearance to the body and the chassis. This does not apply to the spare tire furnished with the vehicle.
It is recommended that new tires be installed in pairs on the same axle.
If it is necessary to replace only 1 tire, pair it with the tire having the most tread to equalize the braking action.
Although they may appear different in tread design, tires built by different manufacturers with identical TPC specifications may be used on the same vehicle.

All Seasons Tires Description
Most vehicles are now equipped with steel-belted all season radial tires as standard equipment. These tires qualify as snow tires, with a 37 percent higher average rating for snow traction than the non-all season radial tires previously used. Other performance areas, such as wet traction, rolling resistance, tread life, and air retention, have also been improved. This was done by improvements in both tread design and tread compounds. These tires are identified by an M + S molded in the tire sidewall following the size number. The suffix MS is also molded in the sidewall after the TPC specification number.

The optional handling tires used on some vehicles are not all season tires. These will not have the MS marking after the tire size or the TPC specification number.

P-Metric Sized Tires Description
All General Motors vehicles now use passenger (P) metric sized tires. P-metric tires are available in 2 load ranges: standard load, 241 kPa (35 psi) maximum, and extra load, 283 kPa (41 psi) maximum. Most passenger vehicle tires are standard load.

Most P-metric tire sizes do not have exact corresponding alphanumeric tire sizes. For example, a P175/70R13 is not exactly equal in size and load-carrying capacity to an FR70-13 For this reason, replacement tires should be of the same TPC specification number as the originals. If P-metric tires must be replaced with other sizes, consult a tire dealer. Tire companies can best recommend the closest match of alphanumeric to P-metric sizes within their own tire lines.

The metric term for measuring tire inflation pressure is the kilopascal (kPa). Tire pressure may be printed in both kPa and psi. One psi equals 6.895 kPa.

See the tire label or refer to Tire and Wheel Specifications for tire inflation pressures.