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 . 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 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.
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.
