Tires: Description and Operation

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).

Tire Inflation Description
This vehicle has been engineered to operate up to the stated load capacity with wheel and tire assemblies of the type, size, construction, and configuration as originally installed. Maintenance of the tire inflation pressures is critical to the continued satisfactory performance, handling, and operating economy of the vehicle. Operation with incorrectly or improperly inflated tires can adversely affect vehicle performance and may contribute to the following:
^ Reduced fuel economy
^ Tire overloading
^ Shortened tire life
^ Excessive tire wear
^ Uneven tire wear
^ Vehicle handling concerns
Inspect the tire pressures when the vehicle has not been driven for at least 3 hours or not more than 1.6 km (1 mi) and when the tires are cool to the touch.

Tire inflation pressures should be inspected monthly and before an extended trip and adjusted to meet the specifications listed for the particular vehicle. Replace any missing or damaged tire valve stem extensions and/or caps to prevent the intrusion of water and contaminates.

One pound per square inch (psi) equals 6.9 kilopascals (kPa). The following table illustrates the conversion of kilopascals to pounds per square inch:





Inflation Pressure Conversion (Kilopascals to PSI)

For the correct inflation pressures refer to the vehicle's tire placard.

Tires inflated to a higher than recommended pressure can contribute to the following conditions:
^ A hard ride
^ Tire bruising
^ Rapid tread wear at the center of the tire
Tires inflated to a lower than recommended pressure can contribute to the following conditions:
^ Tire squeal on turns
^ Hard steering
^ Rapid and/or uneven wear on the outer edges of the tread
^ Tire rim bruises and tire rim rupture
^ Tire cord breakage
^ High tire temperatures
^ Sluggish vehicle handling
^ Higher fuel consumption
Unequal pressure on the same axle can cause the following conditions:
^ Uneven braking action
^ Steering lead
^ Imprecise vehicle handling

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 mi). 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.

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.