Volkswagen Tiguan Owners Manual: Glossary of tire and loading terminology

Read and follow the introductory information and safety information first⇒Introduction to the subject 

Accessory weight

The combined weight (in excess of those standard items which may be replaced) of automatic transmission, electro-mechanical power steering, power brakes, power windows, power seats, radio, and heater, to the extent that these items are available as factory-installed equipment (whether installed or not).

Aspect ratio

The ratio of sidewall height to tire width, expressed as a percentage. A number of 70 (0.7:1 or 70%) or lower indicates a low-profile tire with a shorter sidewall for improved steering response and better overall handling on dry pavement.

Bead

The part of a tire made of steel wires, wrapped or reinforced by ply cords, with the shape and structure to ensure proper fit to the wheel rim.

Bead separation

A breakdown of the bond between components in the bead.

Carcass

The tire structure, except tread and sidewall rubber which, when inflated, bears the load.

Chunking

The breaking away of pieces of the tread or sidewall.

Cord

The strands of material forming the plies in the tire.

Cord Separation

The parting of cords from adjacent rubber compounds.

Cracking

Any parting within the tread, sidewall, or inner liner of the tire extending to cord material.

Cold tire inflation pressure

The tire pressure recommended by the vehicle manufacturer for a tire of a specified size that has not been driven for more than a couple of miles (kilometers) at low speeds in the 3 hour period before the tire pressure is measured or adjusted.

Curb weight

The weight of a motor vehicle with standard equipment including the maximum capacity of fuel, oil, and coolant, air conditioner, and additional weight of optional equipment.

Extra load tire

A tire designed to operate at higher loads and at higher inflation pressures than the corresponding standard tire.

Gross Axle Weight Rating (GAWR)

The load-carrying capacity of a single axle system, measured where the tire contacts the ground.

Gross Vehicle Weight Rating (GVWR)

The maximum loaded weight of the vehicle.

Groove

The space between 2 adjacent tread ribs.

Load rating (code)

The maximum load that a tire is rated to carry for a given inflation pressure. You may not find this information on all tires because it is not required by law.

Maximum load rating

The load rating for a tire at the maximum permissible inflation pressure for that tire.

Maximum loaded vehicle weight

The total of:

• Curb weight.

• Accessory weight.

• Vehicle capacity weight.

• Production options weight.

Maximum (permissible) inflation pressure

The maximum cold inflation pressure to which a tire may be inflated. Also called maximum inflation pressure.

Normal occupant weight

Means 150 lbs (68 kilograms) times the number of occupants seated in the vehicle up to the total seating capacity of your vehicle.

Occupant distribution

The placement of passengers in a vehicle.

Outer diameter

The diameter of a new, properly inflated tire.

Overall width

Total width measured at the exterior sidewalls of an inflated tire, including the additional width of labeling, decorations, or protective bands or ribs.

Passenger car tire

A tire intended for use on passenger cars, multipurpose passenger vehicles, and trucks, that have a gross vehicle weight rating (GVWR) of 10,000 pounds or less.

Ply

A layer of rubber-coated parallel cords. A parting of rubber compound between adjacent plies.

Ply separation

A parting of rubber compound between adjacent plies.

Pneumatic tire

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 5 lbs (2.3 kg) more then the standard items they replace, and not previously considered as curb weight or accessory weight. These include, for example, heavy-duty brakes, ride levelers, heavy-duty battery, and special trim.

Radial ply tires

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

Recommended inflation pressure

The tire pressure recommended by the vehicle manufacturer for a tire of a specified size that has not been driven for more than a couple of miles (kilometers) at low speeds in the 3 hour period before the tire pressure is measured or adjusted.

Reinforced tire

A tire designed to operate at higher loads and at higher inflation pressures than the corresponding standard tire.

Rim

The outer edge of a wheel upon which the tire beads are seated.

Rim diameter

The nominal diameter of the wheel's tire bead seating surface. If you change your wheel size, to wheels of a different diameter, you will have to purchase new tires to match the new wheels.

Rim size

Designation means rim diameter and width.

Rim type designation

The industry or manufacturer's designation for a rim by style or code.

Rim width

The nominal distance between wheel rim flanges.

Section width

The linear distance between the exteriors of the sidewalls of an inflated tire, excluding elevations due to labeling decoration, or protective bands.

Sidewall

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

Sidewall separation

The parting of the rubber compound from the cord material in the sidewall.

Speed rating (letter code)

A standardized letter code indicating the maximum speed at which a tire is designed to be driven for extended periods of time. The ratings range from 93 mph or 150 km/h (P) to 186 mph or (300 km/h) Y.

The speed rating letter code, where applicable, is molded on the tire sidewall ⇒ Speed rating code letter . You may not find this information on all tires because it is not required by law.

Tire Pressure Monitoring System

A system that detects when at least one of a vehicle's tires is underinflated and illuminates a low tire-pressure warning light.

Tread

The portion of a tire that normally touches the road.

Tread rib

A tread section running circumferentially around a tire.

Tread separation

Tire failure caused by the tread pulling away from the tire carcass.

Tread wear indicators (TWI)

Raised areas within the main tread grooves that show, visually, when tires are worn and near the end of their useful life ⇒ Tread depth and tread wear indicators .

Uniform Tire Quality Grading (UTQG)

A tire information system developed by the U.S. National Highway Traffic Safety Administration (NHTSA) that is designed to help buyers compare tires. UTQG is not a safety rating, nor is it a guarantee that a tire will last for a certain number of miles or perform a certain way. It gives tire buyers more information to compare with factors such as price, brand loyalty and dealer recommendations. Under UTQG, tires are graded by the tire manufacturers in 3 areas: tread wear, traction and temperature resistance. UTQG information is molded into the tire sidewalls.

U.S. DOT Tire Identification Number (TIN)

A tire's serial number. It begins with the letters DOT (Department of Transportation) and indicates that the tire meets all federal standards. The next 2 numbers or letters indicate the plant where the tire was manufactured. The last 4 numbers represent the week and year of manufacture.

For example, the numbers 1801 mean that the tire was produced in the 18th week of 2001. Any other numbers are marketing codes used by the tire manufacturer. This information is used to help identify affected consumers if a tire defect requires a recall.

Vehicle capacity weight

The total rated cargo, luggage and passenger load. Passenger load is 150 lbs (68 kilograms) times the vehicle's total seating capacity (as listed on the label inside the driver door).

Vehicle maximum load on the tire

The load on an individual tire that is determined by taking each axle's share of the maximum loaded vehicle weight (GAWR) and dividing by 2.

Vehicle normal load on the tire

The load on an individual tire that is determined by taking each axle's share of the curb weight, accessory weight, and normal occupant weight (distributed according to the table below) and dividing by 2.

Wheel size designation

Wheel rim diameter and width.

Occupant loading and distribution for vehicle normal load for various designated seating capacities