UNIFORM TIRE QUALITY GRADE STANDARD: TREADWAR, TRACTION, AND TEMPERATURE
The Uniform Tire Quality Grade Standard, or UTQG, has three main aspects: Treadwear, Traction, and Temperature.
Treadwear Grades are numbers that indicate how long a tire will last in typical use. They're based on how much the tire wears, as compared with a test tire, over 7,200 miles. A treadwear rating of 100 means that the wear rate is equal to the test tire's wear. A rating of 200 means that the wear rate is double the test tire's wear rate, and so on. While it does not suggest a specific mileage range, it's reasonable to infer that the higher the number, the slower the tire will wear.
Treadwear Grade Examples
|300||Goodyear Eagle F1 GS EMT||2005 Coupe|
|300||Michelin Pilot Super Sport ZP||2014 Stingray|
|220||Goodyear Eagle F1 Supercar||2004 Z06|
|80||Michelin Pilot Sport Cup ZP||'13 ZR1 with PDE performance package|
Keep in mind that the DOT doesn't do across-the-board testing on every tire sold. Rather, the various tire manufacturers test their own, or hire companies to test for them. As the testing may vary between companies, the Treadwear Grade numbers can vary between brands. So if you want to figure out which tires will last longer, your best bet is to compare treadwear ratings between different tires from the same company.
Traction Grades are based on how a tire performs in a straight-line wet skid test. The tires are installed on a "skid trailer," which is pulled at 40 mph over wet asphalt and wet concrete surfaces. The brakes are locked, and braking g forces (the tire's coefficient of friction) are measured to determine the Traction Grade.
Traction Grades are AA for the top-performing tires, A, B, and finally C for the lowest-performing tires.
A couple of notes: Today's highest rating, AA, was only added in 1997. And interestingly enough, Traction Grades have nothing to do with dry braking or cornering, wet cornering, or hydroplaning tests.
Temperature Grades indicate how much heat is generated, or dissipated, by a tire. Testing is done by running an inflated test tire against a large-diameter, high-speed laboratory test wheel. The test tire must operate at a certain speed range, without failure, to earn an A, B, or C grade.
Temperature Grade Standards
|A||Over 115 mph|
|B||Between 100-115 mph|
|C||Between 85-100 mph|
|Note: Don't get the ambiguous Temperature Grade A number of "Over 115 mph" confused with the previously mentioned Speed Rating letters, like a 118-mph "T" speed-rated tire. The Temperature Grades cover a tire's heat-generation and -dissipation abilities only.|
Maximum Inflation Pressure
A tire's maximum inflation pressure is the highest "cold" pressure that a tire is designed to contain. It's located in small print near the tire's bead (close to the wheel), and shown in both kPa and psi.
Note that max pressure is very different than recommended pressure (see the "Corvette Tire Care" sidebar for more info on recommended pressure). Running your tires at max pressure will greatly increase treadwear, while negatively affecting both ride quality and handling.
Materials And Layers
This information tells you what the tread plies and sidewall plies are made of.
Near the max pressure text, you'll see text like this:
Tread: 2 Polyester + 1 Polyamide + 2 Steel
Sidewall: 2 Polyester