Air Pressure The amount of air inside the tyre pressing outward on the tyre. Air pressure is expressed in pounds per square inch (psi) or kilopascal (kPa).

Accessory Weight The combined weight of optional accessories. Some examples of optional accessories are automatic transmission, power seats, and air conditioning.

Aspect Ratio The relationship of a tyre's height to its width.

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

Bead The tyre bead contains steel wires wrapped by steel cords that hold the tyre onto the rim.

Bias Ply Tyre A pneumatic tyre in which the plies are laid at alternate angles less than 90 degrees to the centre line of the tread.

Cold Tyre Pressure The amount of air pressure in a tyre, measured in pounds per square inch (psi) or kilopascals (kPa) before a tyre has built up heat from driving.

Curb Weight The 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 Markings The DOT code includes the Tyre Identification Number (TIN), an alphanumeric designator which can also identify the tyre manufacturer, production plant, brand and date of production.

GVWR Gross Vehicle Weight Rating

GAWR FRT Gross Axle Weight Rating for the Front axle.

GAWR RR Gross Axle Weight Rating for the Rear axle.

Intended Outboard Sidewall The side of an asymmetrical tyre that must always face outward when mounted on a vehicle.

Kilopascal (kPa) The metric unit for air pressure.

Light truck (LT) tyre A tyre designated by its manufacturer as primarily intended for use on lightweight trucks or multipurpose passenger vehicles.

Load ratings The maximum load that a tyre is rated to carry for a given inflation pressure.

Load Index An assigned number ranging from 1 to 279 that corresponds to the load carrying capacity of a tyre.

Maximum Inflation Pressure The maximum air pressure to which a cold tyre may be inflated. The maximum air pressure is molded onto the sidewall.

Maximum Load Rating The load rating for a tyre at the maximum permissible inflation pressure for that tyre.

Maximum Loaded Vehicle Weight The sum of curb weight; accessory weight; vehicle capacity weight; and production options weight.

Normal Occupant Weight The number of occupants a vehicle is designed to seat multiplied by 68 kg (150 lbs.).

Occupant Distribution Designated seating positions.

Outward Facing Sidewall The side of a asymmetrical tyre that has a particular side that faces outward when mounted on a vehicle. The outward facing sidewall bears white lettering or bears manufacturer, brand, and/or model name molding that is higher or deeper than the same moldings on the inner facing sidewall.

Passenger (P-Metric) Tyre A tyre used on passenger cars and some light duty trucks and multipurpose vehicles.

Ply A layer of rubber-coated parallel cords.

Pneumatic tyre A mechanical device made of rubber, chemicals, fabric and steel or other materials, that, when mounted on an automotive wheel, provides the traction and contains the gas or fluid that sustains the load.

Production options weight The combined weight of installed regular production options weighing over 2.3 kg (5 lb.) in excess of the standard items which they replace, not previously considered in curb weight or accessory weight. Examples include heavy duty brakes, ride levelers, roof rack, heavy duty battery, and special trim.

Recommended Inflation Pressure Vehicle manufacturer's recommended tyre inflation pressure and shown on the tyre placard.

Radial Ply Tyre A pneumatic tyre in which the ply cords that extend to the beads are laid at 90 degrees to the centre line of the tread.

Rim A metal support for a tyre and upon which the tyre beads are seated.

Sidewall The portion of a tyre between the tread and the bead.

Speed Rating An alphanumeric code assigned to a tyre indicating the maximum speed at which a tyre can operate.

Traction The friction between the tyre and the road surface. The amount of grip provided.

Tread The portion of a tyre that comes into contact with the road.

Treadwear Indicators Narrow bands, sometimes called "wear bars," that show across the tread of a tyre when only 1.6 mm (2/32 inch) of tread remains.

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

Vehicle Capacity Weight The weight of designated seating positions multiplied by 68 kg (150 lbs.) plus the rated cargo and luggage load.

Vehicle Maximum Load on the Tyre Load on an individual tyre due to curb and accessory weight plus maximum occupant and cargo weight.

Vehicle Normal Load on the Tyre Load on an individual tyre that is determined by distributing to each axle its share of the curb weight, accessory weight, and normal occupant weight and driving by 2.

Vehicle Placard A label permanently attached to a vehicle showing the original equipment tyre size and recommended inflation pressure.