Quick Answer
- 500 A A reads as treadwear 500 (a comparison with a grade 100 tire on the government course, not a mileage), traction A (wet straight-ahead braking) and temperature A.
- Temperature A means the tire completed the 575 rpm stage of NHTSA's laboratory test (about 115 mph on the test wheel). B completed the 500 rpm stage (about 100 mph) but not 575. C did not complete the 500 rpm stage.
- The grade applies to a properly inflated tire that is not overloaded. Winter-type snow tires and temporary spares are not graded.
Enter the marking from the sidewall, such as 500 A A, 340 AA A or TREADWEAR 420 TRACTION A TEMPERATURE B.
Treadwear 500, Traction A, Temperature A
Treadwear
500
About 5 times the wear life of a grade 100 tire on the government test course. A comparison, not a mileage.
Traction
A
Wet braking coefficient more than 0.47 on asphalt and more than 0.35 on concrete. Second highest wet straight-ahead braking grade. Straight-ahead braking only.
Temperature
A
Completes the 575 rpm stage (about 115 mph on the test wheel). A tire may be graded A only if it successfully completes the 575 rpm test stage.
Source: 49 CFR 575.104. The three grades are measured separately, and a tire marked C for traction may have poor traction performance.
Get a plain-English explanation of your results and what they mean for your vehicle.
Tire Temperature Rating Chart: A vs B vs C
The grades differ in the laboratory stage the tire completed. Speeds are calculated from the 67.23-inch test wheel and are test stages, not recommended driving speeds.
| Grade | Laboratory stage | Test wheel speed (calculated) | Share of current tire lines (NHTSA) |
|---|---|---|---|
| A (highest) | Completes the 575 rpm stage | About 115 mph on the test wheel | 62% |
| B (intermediate) | Completes the 500 rpm stage, not the 575 rpm stage | About 100 mph on the test wheel | 34% |
| C (lowest) | Fails to complete the 500 rpm stage | Below about 100 mph on the test wheel | 4% |
Source: NHTSA, 49 CFR 575.104. NHTSA says grade C corresponds to the level all passenger car tires must meet under FMVSS No. 109 and that grades B and A are higher levels of performance on the test wheel. The grade applies to a properly inflated tire that is not overloaded.
What 500 A A and 340 A A Mean on a Tire
Reading the sidewall
- 1Look at the outer sidewall between the tread shoulder and the maximum section width. NHTSA says the grades are molded there.
- 2Find the three grades. They can be written in full, as in TREADWEAR 500 TRACTION A TEMPERATURE A, or as a short form such as 500 A A.
- 3Read them in order: the number is treadwear, the first letter is traction and the last letter is temperature.
- 4For the temperature grade, look at the last letter: A is the highest, then B, then C.
- 5If there is no UTQG marking, the tire may be one the rule does not cover: a deep tread tire, winter-type snow tire, temporary spare, tire with a rim diameter of 12 inches or less, or a limited production tire.
In TREADWEAR 500 TRACTION A TEMPERATURE A and in TREADWEAR 340 TRACTION A TEMPERATURE A the last A is the temperature grade. The three grades are measured separately, so Temperature A says nothing about wear or braking.
Traction grades: AA vs A vs B vs C
Adjusted wet braking coefficients on the government asphalt and concrete test surfaces, tested straight ahead.
| Traction grade | Asphalt | Concrete | Note |
|---|---|---|---|
| AA | More than 0.54 | More than 0.38 | The highest wet straight-ahead braking grade. |
| A | More than 0.47 | More than 0.35 | Second highest wet straight-ahead braking grade. |
| B | More than 0.38 | More than 0.26 | Middle wet straight-ahead braking grade. |
| C | 0.38 or less | 0.26 or less | NHTSA says a tire marked C may have poor traction performance. |
For grade C the tire fails either surface. NHTSA warns the traction grade does not include acceleration, cornering, hydroplaning or peak traction. More on the treadwear and traction grades is on the treadwear and traction grade explainer.
Treadwear grade chart
NHTSA says the treadwear grade is a comparative rating: a tire graded 150 wears one and one-half times as well on the government course as a tire graded 100. It is not a mileage, and grades are multiples of 20.
| Treadwear grade | Wear life compared with grade 100 (calculated) |
|---|---|
| 200 | 2 times |
| 300 | 3 times |
| 340 | 3.4 times |
| 400 | 4 times |
| 420 | 4.2 times |
| 460 | 4.6 times |
| 500 | 5 times |
| 540 | 5.4 times |
| 600 | 6 times |
| 640 | 6.4 times |
| 800 | 8 times |
NHTSA adds that the relative performance of tires depends on actual conditions of use and may depart significantly from the norm because of driving habits, service practices, road characteristics and climate.
How UTQG Temperature Grades Are Assigned
The laboratory test
- 1The tire is mounted on a rim of the design or measuring width for its size and inflated to the pressure the rule specifies.
- 2It is kept at 95 °F for at least 3 hours, the pressure is adjusted again, and the ambient air stays at 95 °F during the test.
- 3The tire is pressed against a flat-faced steel test wheel 67.23 inches in diameter with a load of 88% of its maximum load rating.
- 4The wheel turns at 250 rpm for 2 hours. The load is removed, the tire cools and the pressure is reset.
- 5The load is reapplied and the wheel turns at 375 rpm for 30 minutes, then in 25 rpm steps of 30 minutes each, up to 575 rpm or until the tire fails.
- 6A stage counts as completed if the tire shows no visual evidence of tread, sidewall, ply, cord, innerliner or bead separation, chunking, broken cords, cracking or open splices, and its pressure is not below the specified minimum.
A tire that completes the 575 rpm stage is graded A. One that completes the 500 rpm stage but not 575 is graded B. A tire that fails the 500 rpm stage is graded C.
Tires without a UTQG grade
| Tire type not covered by 49 CFR 575.104 |
|---|
| Deep tread tires |
| Winter-type snow tires |
| Space-saver or temporary use spare tires |
| Tires with nominal rim diameters of 12 inches or less |
| Limited production tires |
The rule applies to new pneumatic tires for passenger cars. A limited production tire is one made or imported in small numbers as defined in the rule.
What Raises Tire Temperature
A temperature grade is assigned under controlled conditions. NHTSA names these as causes of heat buildup and possible tire failure.
Speed
NHTSA says excessive speed can cause heat buildup and possible tire failure.
Tip: Follow the speed rating your vehicle manufacturer specifies. A speed rating is not a recommended travel speed (Bridgestone).
Underinflation
NHTSA says underinflation can cause heat buildup and possible tire failure.
Tip: Check cold pressure at least monthly against the Tire and Loading Information Label (NHTSA).
Overloading
NHTSA says overloading can cause heat buildup and possible tire failure.
Tip: Do not exceed the load capacity on the vehicle placard. Michelin says a lower load index than the factory specification should never be fitted.
Hot weather and long distances
NHTSA says sustained high temperature, for example driving long distances in hot weather, can cause a tire to deteriorate, leading to blowouts and tread separation.
Tip: Keep pressure at the recommended cold value and check tires before long trips.
Temperature grade and your driving situation
What the manufacturers and NHTSA say for each situation. They do not set a required temperature grade, so follow your vehicle manufacturer's tire specification.
| Your situation | What the sources say |
|---|---|
| Towing a trailer | Ford's towing guide says underinflated tires get hot and may fail, and that tires should be checked often against the recommended cold inflation pressures. Follow the vehicle and trailer manuals for tire load and pressure. |
| Performance or sports car | Follow the vehicle manufacturer's specified size, load index and speed rating. Michelin says replacement tires should meet or exceed the specified speed rating. |
| Heavy loads | NHTSA says overloading can cause heat buildup and possible tire failure. Stay within the load capacity on the tire placard. |
| Hot weather, long highway trips | NHTSA says sustained high temperature, such as driving long distances in hot weather, can cause a tire to deteriorate, leading to blowouts and tread separation. |
| Winter and snow tires | 49 CFR 575.104 does not apply to winter-type snow tires, so the temperature grade may not appear on them. |
Temperature Rating vs Speed Rating
They are related but not the same. The speed letter is looked up on the speed rating chart in mph and km/h, and the maximum load for a tire is on the load index chart.
| Aspect | Temperature rating (A, B, C) | Speed rating |
|---|---|---|
| What it measures | Resistance to heat generation and ability to dissipate heat on a laboratory test wheel (NHTSA) | Michelin: the maximum speed at which a tire can carry its maximum load under specified conditions |
| Grading scale | A (highest), B, C | Letters such as S, T, H, V, W, Y |
| Where it is on the tire | UTQG marking: TEMPERATURE A, B or C | End of the service description, for example 225/55R17 97V, where V is the speed symbol |
| Applies to all tires? | No, the exempt tire types are listed above | Appears in the service description of most passenger tires |
Pressure units are converted on the kPa to PSI page.
How to Use the Tire Temperature Rating Decoder
- 1Find the UTQG marking on the sidewall. It reads like TREADWEAR 500 TRACTION A TEMPERATURE A, or 500 A A in short form.
- 2In Decode a Tire Marking, type it in. You get the treadwear comparison, the traction grade with its braking coefficients and the temperature grade with its laboratory stage.
- 3To compare grades without a tire, open Compare Temperature Grades and pick A, B or C.
- 4Compare the grades only after matching the size, load index and speed rating your vehicle manufacturer specifies.