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
than the standard items they replace, and not previously considered as curb weight or accessory weight. These include, for
example, heavy-duty brakes, ride levelers, roof rack, 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 pressu
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 (150 km/h) “P” to 186 mph (300 km/h) “Y”. The speed rating lette
code, where applicable, is molded on the tire sidewall. 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.
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 factor
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
1709 mean that the tire was produced in the 17th week of 2009. 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.
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