Mercedes-Benz GLC : Wheels and tires / Definition of terms for tires and loading

Tire structure and characteristics: describes the number of layers or the number of rubbercoated belts in the tire contact surface and the tire wall. These are made of steel, nylon, polyester and other materials.

Bar: metric unit for tire pressure. 14.5038 pounds per square inch (psi) and 100 kilopascal (kPa) is the equivalent of one bar.

DOT (Department of Transportation): DOTmarked tires fulfill the requirements of the US Department of Transportation.

Average weight of the vehicle occupants: the number of vehicle occupants for which the vehicle is designed, multiplied by 150 lb (68 kg).

Uniform Tire Quality Grading Standards: a uniform standard to grade the quality of tires with regard to tread quality, tire traction and temperature characteristics. The quality grading assessment is made by the manufacturer following specifications from the U.S. government. The quality grade of a tire is imprinted on the side wall of the tire.

Recommended tire pressure: the recommended tire pressure is the tire pressure specified for the tires mounted to the vehicle at the factory.

The tire and information table contains the recommended tire pressures for cold tires, the maximum permissible load and the maximum permissible vehicle speed.

The tire pressure table contains the recommended tire pressures for cold tires under various operating conditions, i.e. loading and/or speed of the vehicle.

Increased vehicle weight due to optional equipment: the combined weight of all standard and optional equipment available for the vehicle, regardless of whether it is actually installed on the vehicle or not.

Rim: the part of the wheel on which the tire is installed.

GAWR (Gross Axle Weight Rating): the GAWR is the maximum permissible axle load. The actual load on an axle must never exceed the gross axle weight rating. The gross axle weight rating can be found on the vehicle identification plate on the B‑pillar on the driver's side.

Speed rating: the speed rating is part of the tire identification. It specifies the speed range for which a tire is approved.

GVW (Gross Vehicle Weight): the gross vehicle weight comprises the weight of the vehicle including fuel, tools, the spare wheel, accessories installed, occupants, luggage and the trailer drawbar noseweight, if applicable. The gross vehicle weight must not exceed the gross vehicle weight rating GVWR as specified on the vehicle identification plate on the B‑pillar on the driver's side.

GVWR (Gross Vehicle Weight Rating): the GVWR is the maximum permitted gross weight of the fully laden vehicle (weight of the vehicle including all accessories, occupants, fuel, luggage and the trailer drawbar noseweight if applicable). The gross vehicle weight rating is specified on the vehicle identification plate on the B‑pillar on the driver's side.

Maximum weight of the laden vehicle: the maximum weight is the sum of the curb weight of the vehicle, the weight of the accessories, the maximum load and the weight of optional equipment installed at the factory.

Kilopascal (kPa): metric unit for tire pressure. 6.9 kPa corresponds to 1 psi. Another unit for tire pressure is bar. 100 kilopascal (kPa) equals 1 bar.

Load index: in addition to the load-bearing index, the load index may also be imprinted on the side wall of the tire. This specifies the loadbearing capacity of the tire more precisely.

Curb weight: the weight of a vehicle with standard equipment including the maximum capacity of fuel, oil and coolant. It also includes the air conditioning system and optional equipment if these are installed on the vehicle, but does not include passengers or luggage.

Maximum tire load: the maximum tire load is the maximum permissible weight in kilograms or lbs for which a tire is approved.

Maximum permissible tire pressure: maximum permissible tire pressure for one tire.

Maximum load on one tire: maximum load on one tire. This is calculated by dividing the maximum axle load of one axle by two.

PSI (pounds per square inch): standard unit of measurement for tire pressure.

Aspect ratio: ratio between tire height and tire width in percent.

Tire pressure: pressure inside the tire applying an outward force to every square inch of the tire. The tire pressure is specified in pounds per square inch (psi), in kilopascals (kPa) or in bar. The tire pressure should only be corrected when the tires are cold.

Cold tire pressure: the tires are cold when the vehicle has been parked for at least 3 hours without direct sunlight on the tires or the vehicle has been driven for less than 1 mile (1.6 km).

Tire contact surface: the part of the tire that comes into contact with the road.

Tire bead: the purpose of the tire bead is to ensure that the tire sits securely on the wheel rim. There are several wire cores in the tire bead to prevent the tire from changing length on the wheel rim.

Side wall: the part of the tire between the tread and the tire bead.

Weight of optional equipment: the combined weight of the optional equipment weighing more than the replaced standard parts and more than 5 lbs (2.3 kg). This optional equipment, such as high-performance brakes, level control system, a roof luggage rack or high-performance batteries, is not included in the curb weight and the weight of the accessories.

TIN (Tire Identification Number): a unique identification number which can be used by a tire manufacturer to identify tires, for example, in a product recall, and thus identify the purchasers. The TIN is made up of the manufacturer's identity code, tire size, tire type code and the manufacturing date.

Load-bearing index: the load-bearing index is a code that contains the maximum load-bearing capacity of a tire.

Traction: traction is the grip resulting from friction between the tires and the road surface.

Wear indicator: narrow bars (tread wear bars) that are distributed over the tire contact surface. If the tire tread is level with the bars, the wear limit of 1/16 in (1.6 mm) has been reached.

Distribution of vehicle occupants: distribution of vehicle occupants over designated seat positions in a vehicle.

Maximum permissible payload weight: nominal load and luggage load plus 150 lb (68 kg) multiplied by the number of seats in the vehicle.