Wheels and Tires: Description and Operation

General Description
The factory installed tires are designed to operate satisfactorily with loads up to and including the full rated load capacity when these tires are inflated to the recommended pressures.

The following factors have an important influence on tire life:
^ Correct tire pressures Correct wheel alignment
^ Proper driving techniques
^ Tire rotation

The following factors increase tire wear:
^ Heavy cornering
^ Excessively rapid acceleration
^ Heavy braking

Tread Wear Indicators Description





The original equipment tires have tread wear indicators that show when you should replace the tires.

The location of these indicators are at 72 degree intervals around the outer diameter of the tire. The indicators appear as a 6 mm (0.25 inch) wide band when the tire tread depth becomes 1.6 mm (2/32 inch).

Metric Wheel Nuts and Bolts Description
Metric wheel/nuts and bolts are identified in the following way:
^ The wheel/nut has the word Metric stamped on the face.
^ The letter M is stamped on the end of the wheel bolt.

The thread sizes of metric wheel/nuts and the bolts are indicated by the following example: M12 x 1.5.
^ M = Metric
^ 12 = Diameter in millimeters
^ 15 = Millimeters gap per thread

Tire Inflation Description
When you inflate the tires to the recommended inflation pressures, the factory-installed wheels and tires are designed in order to handle loads to the tire's rated load capacity. Incorrect tire pressures, or under-inflated tires, can cause the following conditions:
^ Vehicle handling concerns
^ Poor fuel economy
^ Shortened tire life
^ Tire overloading

Inspect the tire pressure when the following conditions apply:
^ The vehicle has been sitting at least 3 hours.
^ The vehicle has not been driven for more than 1.6 km (1 ml).
^ The tires are cool.

Inspect the tires monthly or before any extended trip. Adjust the tire pressure to the specifications on the tire label. Install the valve caps or the extensions on the valves. The caps or the extensions keep out dust and water.

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





Inflation Pressure Conversion (Kilopascals to PSI)

Tires with a higher than recommended pressure can cause the following conditions:
^ A hard ride
^ Tire bruising
^ Rapid tread wear at the center of the tire

Tires with a lower than recommended pressure can cause the following conditions:
^ A tire squeal on turns
^ Hard steering
^ Rapid wear and uneven wear on the edge of the tread
^ Tire rim bruises and tire rim rupture
^ Tire cord breakage
^ High tire temperatures
^ Reduced vehicle handling
^ High fuel consumption
^ Soft riding

Unequal pressure on the same axle can cause the following conditions:
^ Uneven braking
^ Steering lead
^ Reduced vehicle handling

Refer to the Tire Placard for specific tire and wheel applications and tire pressures.

Tire Chain Usage Description





When you use tire chains, most current vehicles require the following chain types:
^ SAE Class S or 1100 Series, Type PL tire chains (1)
^ SAE Class U or 1200 Series, Type P tire chains (2)
^ 1800 Series Lug Reinforced tire chains (3)

These chains are specially designed in order 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.

The use of chains may adversely affect handling. When using chains! remember the following information:
^ Ensure that the vehicle is designed for chain clearance.
^ Adjust the speed to road conditions.
^ Avoid sharp turns.
^ Avoid locked-wheel braking in order to prevent chain damage to the vehicle.
^ Install the chains as tightly as possible on the drive tires. Tighten the chains again after driving 0.4-0.8 km (0.25-0.5 ml). Do not use chains on the non-drive tires. These chains may contact and damage the vehicle. If you use chains on the non-drive tires. ensure that there is enough clearance.
^ Do not exceed 70 km/h (45 mph). Do not exceed the chain manufacturer's speed limit, if lower.
^ Drive in a restrained manner. Avoid large bumps, potholes, severe turns, and other maneuvers that cause the tires to bounce up and down.
^ Follow any other instructions from the chain manufacturer that do not disagree with the above.

Tire Description

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.





This vehicle is equipped with speed rated tires. Listed below are the common speed rating symbols and the corresponding maximum speeds:

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

The following is required of replacement tires:
^ Replacement tires must be of the same size as the original tires.
^ Replacement tires must be of the same speed rating as the original tires.
^ Replacement tires must be of the same load index as the original tires.
^ Replacement tires must be of the same construction as the original tires.
^ Replacement tires must have the same TPC specification number as the original tires.

The following may seriously be affected by the use of any other tire size, tire speed rating or tire type:
^ May seriously affect the ride.
^ May seriously affect the handling.
^ May seriously affect the speedometer/odometer calibration.
^ May seriously affect the antilock brake system.
^ May seriously affect the vehicle ground clearance.
^ May seriously affect the trailering capacity.
^ May seriously affect the tire clearance to the body.
^ May seriously affect the tire clearance to the chassis.

Conditions for Tire Replacement
Replace the tires when one and/or all of the following conditions are evident:
^ When the tire(s) is worn to a point where 1.6 mm (2/32 inch) or less of tread remains. The tires have built in tread wear indicators that appear between the tread grooves when the tread is worn to 1.6 mm (2/32 inch) or less to help in the detection of this condition. Replace the tire when the indicators appear in two or more adjacent grooves at three spots around the tire.
^ When the following conditions are evident on the tread:
- When the tread is cracked.
- When the tread is cut.
- When the tread is snagged deeply enough to expose the cord.
- When the tread is snagged deeply enough to expose the fabric.
- When the sidewall is snagged deeply enough to expose the cord.
- When the sidewall is snagged deeply enough to expose the fabric.
^ When the following conditions are evident on the tire:
- When the tire has a bump.
- When the tire has a bulge (protrusion).
- When the tire is split.
- Please note that slight sidewall indentations are normal in radial tires.
^ When the following damage is evident on the tire and the damage cannot be correctly repaired because of the size or the location of the damage:
- When the tire has a puncture.
- When the tire is cut, or other damage.

Always install new tires in pairs on the same axle. In the event that only one tire is replaced, then pair with the tire having the most tread.

All Seasons Tires Description





Most GM vehicles are equipped with steel belted all-season radial tires as standard equipment. These tires qualify as snow tires, with a higher than 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, are also improved. This is done by improvements in both tread design and tread compounds. These tires are identified by an M + S molded in the tire side wall after the tire size. The suffix MS is also molded in the tire side wall after the TPC specification number.

The optional handling tires used on some vehicles now also have the MS marking after the tire size and the TPC specification number.

P-metric Sized Tires Description





Most P-metric tire sizes do not have exact corresponding alphanumeric tire sizes. Replacement tires should be of the same tire performance criteria (TPC) specification number including the same size, the same load range, and the same construction as those originally installed on the vehicle. Consult a tire dealer if you must replace the P-metric tire with other sizes. Tire companies can best recommend the closest match of alphanumeric to P-metric sizes within their own tire lines.

Replacement Wheels Description
Replace the wheel if any of the following conditions exist:
^ The wheel exhibits excessive runout.
^ The wheel is bent.
^ The wheel is cracked.
^ The wheel is severely rusted.
^ The wheel is severely corroded.

Important: Air leaks caused by porosity on aluminum wheels are repairable.

^ The wheel leaks air.

Caution: If you are replacing the wheel(s), the wheel stud(s), the wheel nut(s) or the wheel bolt(s), install only new GM original equipment parts. Installation of used parts or non-GM original equipment parts may cause the wheel to loosen, loss of tire air pressure, poor vehicle handling and loss of vehicle control resulting in personal injury.

Notice: The use of non-GM original equipment wheels may cause:
^ Damage to the wheel bearing, the wheel fasteners and the wheel
^ Tire damage caused by the modified clearance to the adjacent vehicle components
^ Adverse vehicle steering stability caused by the modified scrub radius
^ Damage to the vehicle caused by the modified ground clearance
^ Speedometer and odometer inaccuracy

Replace the wheel, the wheel studs and the wheel/nuts, or the wheel bolts if applicable, if any of the following conditions exist:
^ The wheel has elongated bolt holes.
^ The wheel/nuts, or bolts if applicable, loosen repeatedly.

Steel wheel identification is stamped into the wheel near the valve stem.

Aluminum wheel identification is cast into the inboard side of the wheel.