Audi A4: Glossary of tire and loading terminology

Accessory weight

means the combined weight (in excess of those standard items which may be replaced) of automatic transmission, 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

means the ratio of the height to the width of the tire in percent.

Numbers of 55 or lower indicate a low sidewall for improved steering response and better overall handling on dry pavement.

Bead

means the part of the tire that is made of steel wires, wrapped or reinforced by ply cords and that is shaped to fit the rim.

Bead separation

means a breakdown of the bond between components in the bead.

Cord

means the strands forming the plies in the tire.

Cold tire inflation pressure

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

Curb weight

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

Extra load tire

means a tire designed to operate at higher loads and at higher inflation pressures than the corresponding standard tire. Extra load tires may be identified as "XL", "xl", "EXTRA LOAD", or "RF" on the sidewall.

Gross Axle Weight Rating ("GAWR")

means the load-carrying capacity of a single axle system, measured at the tire-ground interfaces.

Gross Vehicle Weight Rating ("GVWR")

means the maximum total loaded weight of the vehicle.

Groove

means the space between two adjacent tread ribs.

Load rating (code)

means 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

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

Maximum loaded vehicle weight

means the sum of:

1.  Curb weight
2.  Accessory weight
3.  Vehicle capacity weight, and
4.  Production options weight

Maximum (permissible) inflation pressure

means 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

means distribution of occupants in a vehicle.

Outer diameter

means the overall diameter of an inflated new tire.

Overall width

means the linear distance between the exteriors of the sidewalls of an inflated tire, including elevations due to labeling, decorations, or protective bands or ribs.

Ply

means a layer of rubber-coated parallel cords.

Production options weight

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

Radial ply tire

means 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

see Cold tire inflation pressure.

Reinforced tire

means a tire designed to operate at higher loads and at higher inflation pressures than the corresponding standard tire. Reinforced tires may be identified as "XL", "xl", "EXTRA LOAD", or "RF" on the sidewall.

Rim

means a metal support for a tire or a tire and tube assembly upon which the tire beads are seated.

Rim diameter

means nominal diameter of the bead seat. If you change your wheel size, you will have to purchase new tires to match the new rim diameter.

Rim size designation

means rim diameter and width.

Rim width

means nominal distance between rim flanges.

Sidewall

means that portion of a tire between the tread and bead.

Speed rating (letter code)

means the speed at which a tire is designed to be driven for extended periods of time. The ratings range from 93 mph (150 km/h) to 186 mph (298 km/h) > table. You may not find this information on all tires because it is not required by law.

The speed rating letter code, where applicable, is molded on the tire sidewall and indicates the maximum permissible road speeds.

Tire pressure monitoring system

means a system that detects when one or more of a vehicle's tires are underinflated and illuminates a low tire pressure warning telltale.

Tread

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

Tread separation

means pulling away of the tread from the tire carcass.

Treadwear indicators (TWI)

means the projections within the principal grooves designed to give a visual indication of the degrees of wear of the tread. See Treadwear indicator for more information on measuring tire wear.

Uniform Tire Quality Grading

is a tire information system developed by the United States National Highway Traffic Safety Administration (NHTSA) that is designed to help buyers make relative comparisons among tires. The UTQG is not a safety rating and not a guarantee that a tire will last fora prescribed number of miles (kilometers) or perform in a certain way. It simply gives tire buyers additional information to combine with other considerations, such as price, brand loyalty and dealer recommendations. Under UTQG, tires are graded by the tire manufacturers in three areas: treadwear, traction, and temperature resistance. The UTQG information on the tires, molded into the sidewalls.

U.S. DOT Tire Identification Number (TIN)

This is the tire's "serial number".

It begins with the letters "DOT" and indicates that the tire meets all federal standards. The next two numbers or letters indicate the plant where it was manufactured, and the last four numbers represent the week and year of manufacture. For example,

DOT... 2221...

means that the tire was produced in the 22nd week of 2021. The other numbers are marketing codes that may or may not beused by the tire manufacturer. This information is used to contact consumers if a tire defect requires a recall.

Vehicle capacity weight

means the rated cargo and luggage load plus 150 lbs. (68 kilograms) times the vehicle's designated seating capacity.

Vehicle maximum load on the tire

means that load on an individual tire that is determined by distributing to each axle its share of the maximum loaded vehicle weight and dividing by two.

Vehicle normal load on the tire

means that load on an individual tire that is determined by distributing to each axle its share of the curb weight, accessory weight, and normal occupant weight (distributed in accordance with > table) and dividing by two.

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

Refer to the tire inflation pressure label fig. 167 for the number of seating positions.

Refer to the table for the number of people that correspond to the vehicle normal load.

READ NEXT: