A tyre's treadwear is one of the three standards measured by the UTQG. The other two standards are: tyre traction grade and resistance to heat while driving.
These three grades are marked on the sidewall of your tyres and are there to give you information about the performance of your tyres.
What is UTQG?
The UTQG is a rating system set out by the US National Highway Traffic Safety Administration. All tyres on the road in the United States are required to have the ratings on their sidewalls. As tyre manufacturers produce all over the world, the vast majority of tyres on the road in Europe feature these markings. Although, it isn't a legal requirement in Europe.
Definition of tyre treadwear
Treadwear indicates how worn your tyre's tread is. Although it's difficult to accurately say exactly how many miles you'll be able to drive with your tyres, they can be tested based on a universal and standardised protocol to evaluate them, and possibly compare them based on this grading.
The results of these tests are represented by 3 figures. The higher the treadwear grade of the tyre, the longer it will last, and the more miles it will be able to travel. On the other hand, the lower the treadwear grade, the more quickly the tyre will wear out.
So, a tyre with a treadwear of 600 will theoretically last 3x longer than a tyre with a treadwear of 200.
Ratings to compare tyre treadwear
The treadwear grade starts below 100 and can rise to over 700.
It's worth noting two important elements:
- The test consists of covering approximately 7,200 miles on a standardised course in the United States, then predicting longevity according to the results obtained.
- Only the manufacturer performs these tyre tests, and they are not monitored by an independent body.
For these reasons, comparing the different treadwear grades from different tyre brands can quickly become inaccurate, or even confusing.
Some say that the result of a tyre's treadwear is a clever combination put together by specialist engineers and marketing teams in search of a good sales pitch.
The tyre's traction grade
Implemented several years before the European label, the tyre's traction is tested by fitting it to a trailer axle travelling at a constant speed in the rain with a series of stops. Several types of ground (tarmac and concrete) feature in the test session.
The closer the rating is to AA, the better the traction of the tyre.
Here's a scoring table outlining the traction performance of your tyres:
| Traction grade | G-force coefficient on tarmac | G-force coefficient on concrete |
|---|---|---|
| AA | >0.54 | 0.38 |
| A | 0.47<Coef<0.54 | 0.35 |
| B | 0.38<Coef<0.47 | 0.26 |
| C | <0.38 | 0.26 |
Tyre temperature grade
When you're driving on your tyre, it's in contact with the ground, resulting in friction. Its temperature increases according to several elements such as:
- The weight being carried
- Your driving speed
- The power of your vehicle
- The type of ground
- The outside temperature
- The ground temperature
- Etc.
The design of the tyre and the rubber compound mean that, depending on the variables mentioned above, every tyre will heat up differently.
The test is carried out in the lab to determine the speed at which the tyre will start to deteriorate at a constant rate.
The given rating is indicated by a letter corresponding to:
| Sidewall lettering | Maximum speed before deterioration |
|---|---|
| A | >115 mph |
| B | 100 mph < Test < 115 mph |
| C | 85 mph < Test < 100 mph |
While these tests and grades may seem redundant with other indicators such as the European tyre label or the tyre speed index, they're still used for all approvals in the United States and by many European users eager to get information on tyres.
