GM Service Manual Online
For 1990-2009 cars only
Air PressureThe amount of air inside the tire pressing outward on each square inch of the tire. Air pressure is expressed in pounds per square inch (psi) or kilopascal (kPa).

Accessory WeightThis means the combined weight of optional accessories. Some examples of optional accessories are, automatic transmission, power steering, power brakes, power windows, power seats, and air conditioning.

Aspect RatioThe relationship of a tire's height to its width.

BeltA rubber coated layer of cords that is located between the plies and the tread. Cords may be made from steel or other reinforcing materials.

BeadThe tire bead contains steel wires wrapped by steel cords that hold the tire onto the rim.

Bias Ply TireA pneumatic tire in which the plies are laid at alternate angles less than 90 degrees to the centerline of the tread.

Cold Tire PressureThe amount of air pressure in a tire, measured in pounds per square inch (psi) or kilopascals (kPa) before a tire has built up heat from driving. See Inflation - Tire Pressure .

Curb WeightThe weight of a motor vehicle with standard and optional equipment including the maximum capacity of fuel, oil, and coolant, but without passengers and cargo.

DOT MarkingsA code molded into the sidewall of a tire signifying that the tire is in compliance with the U.S. Department of Transportation (DOT) motor vehicle safety standards. The DOT code includes the Tire Identification Number (TIN), an alphanumeric designator which can also identify the tire manufacturer, production plant, brand, and date of production.

GVWRGross Vehicle Weight Rating. See Loading the Vehicle .

GAWR FRTGross Axle Weight Rating for the front axle. See Loading the Vehicle .

GAWR RRGross Axle Weight Rating for the rear axle. See Loading the Vehicle .

Intended Outboard SidewallThe side of an asymmetrical tire, that must always face outward when mounted on a vehicle.

Kilopascal (kPa)The metric unit for air pressure.

Light Truck (LT-Metric) TireA tire used on light duty trucks and some multipurpose passenger vehicles.

Load IndexAn assigned number ranging from 1 to 279 that corresponds to the load carrying capacity of a tire.

Maximum Inflation PressureThe maximum air pressure to which a cold tire can be inflated. The maximum air pressure is molded onto the sidewall.

Maximum Load RatingThe load rating for a tire at the maximum permissible inflation pressure for that tire.

Maximum Loaded Vehicle WeightThe sum of curb weight, accessory weight, vehicle capacity weight, and production options weight.

Normal Occupant WeightThe number of occupants a vehicle is designed to seat multiplied by 150 lbs (68 kg). See Loading the Vehicle .

Occupant DistributionDesignated seating positions.

Outward Facing SidewallThe side of an asymmetrical tire that has a particular side that faces outward when mounted on a vehicle. The side of the tire that contains a whitewall, bears white lettering, or bears manufacturer, brand, and/or model name molding that is higher or deeper than the same moldings on the other sidewall of the tire.

Passenger (P-Metric) TireA tire used on passenger cars and some light duty trucks and multipurpose vehicles.

Recommended Inflation PressureVehicle manufacturer's recommended tire inflation pressure as shown on the tire placard. See Inflation - Tire Pressure and Loading the Vehicle .

Radial Ply TireA pneumatic tire in which the ply cords that extend to the beads are laid at 90 degrees to the centerline of the tread.

RimA metal support for a tire and upon which the tire beads are seated.

SidewallThe portion of a tire between the tread and the bead.

Speed RatingAn alphanumeric code assigned to a tire indicating the maximum speed at which a tire can operate.

TractionThe friction between the tire and the road surface. The amount of grip provided.

TreadThe portion of a tire that comes into contact with the road.

Treadwear IndicatorsNarrow bands, sometimes called wear bars, that show across the tread of a tire when only 1/16 inch (1.6 mm) of tread remains. See When It Is Time for New Tires .

UTQGS (Uniform Tire Quality Grading Standards)A tire information system that provides consumers with ratings for a tire's traction, temperature, and treadwear. Ratings are determined by tire manufacturers using government testing procedures. The ratings are molded into the sidewall of the tire. See Uniform Tire Quality Grading .

Vehicle Capacity WeightThe number of designated seating positions multiplied by 150 lbs (68 kg) plus the rated cargo load. See Loading the Vehicle .

Vehicle Maximum Load on the TireLoad on an individual tire due to curb weight, accessory weight, occupant weight, and cargo weight.

Vehicle PlacardA label permanently attached to a vehicle showing the vehicle's capacity weight and the original equipment tire size and recommended inflation pressure. See "Tire and Loading Information Label" under Loading the Vehicle .