Tire Tread Rating Question

[Bonkers]

Our Pilots have a UTQG rating of 220. I was looking at another set of tires with a UTQG rating of 140.

Two questions -
- Exactly how do UTQG numbers relate to each other? I know a lower number means shorter life, but is there a way to quantify it in terms of miles?

- The reason I'm asking - If the pilots make it 15,000 miles @ 220 how long should the 140s be expected to last?

 

[Ron]

9545 miles.

It's a relative measurement with 100 being "normal". For example, 220 is 2.2 times better than a 100, 140 is 1.4 times better than a 100, 220 is 57% better than a 140.

There is no specific mileage claim on the baseline "100". Too many other variables, road temp, car weight, avg. vehicle speed, etc.

 

[Randy]

I heard a rumor that there isn't really any "standard" on how to figure the treadwear especially between different manufacturers, so its only vaguely related to treadwear, and is not necessarily comparable to another manufacturers treadwear rating.

Similarly, check the "traction" rating of the Pilot Sports, and compare them to tires like the Hoosier R3S04s, etc. According to those ratings, the Pilot Sports (traction AA) are stickier than tht Hoosiers (traction C), which would seem to be exactly opposite.

 

[Ron]

The numbers do represent relative tire life regardless of brand as they all have to develop their numbers on the same government designated test course...

Treadwear
Treadwear grades typically range from 60 to over 500, in twenty point increments. It's important to remember that the actual life of any tire is determined by the road surface quality, driving habits, inflation, wheel alignment and the rotation it experiences. To receive a treadwear grade, a tire is tested under controlled conditions on a government prescribed test course which does not necessarily simulate the actual application for which a given tire is designed to perform. As a result of these test parameters, there is no reliable way to assign miles of wear to treadwear grade points.

Treadwear ratings are determined on a 400 mile government test course covering specified sections of public roads near San Angelo, Texas. A group of not more than four test vehicles travels the course in a convoy so that all tires experience the same conditions. Tread groove depths of the tires being tested are measured after each 800 miles. The same procedure is followed for a set of control or "course monitoring tires".Upon completion of the 7200 mile test, the rating results of both tests are compared, and the tires being tested are assigned a treadwear rating by the tire manufacturer.

The best way to use treadwear ratings when buying tires is to compare one rating to another. For instance, a tire with a treadwear grade of 400 might be expected to last twice as long as a tire that has a grade of 200.

Regarding Traction:
Traction grades indicate the measurement of a tire's ability to stop a car in straight-ahead motion on a wet test surface pavement (hence the reason why Pilots have a higher number then Hoosiers). It does not measure straight-ahead acceleration. It's important to remember that traction rating tests are performed only for straight-ahead sliding on concrete and asphalt surfaces that have a specified degree of wetting which simulates most road surfaces in a rainstorm. The ratings that result from these tests may not apply to cornering traction or peak values of straight-ahead braking forcelike those experienced in non-skid braking tests. Traction grades range from "A" to "C", with "A" being the highest attainable grade.

Traction ratings are established on government maintained skid pads. Twenty measurements are taken with an industry standard control tire on an asphalt surface and averaged. the same number of measurements are made on a concrete surface. Corresponding measurements are then made on the tires being tested. Once the results of the tests are compared, traction ratings based on government prescribed coefficient levels are assigned to the tires that were tested.

And to complete the picture, temperature:
Temperature grades also range from "A" to "C", with A being the highest. Temperature grades represent a properly maintained tire's ability to dissipate heat under controlled indoor test wheel conditions.

Temperature ratings are determined by running tires on an indoor roadwheel test under specified conditions. Successive 30 minute runs are made in 5 mph increments starting at 75 mph and continuing until the tire fails. A tire is graded "C" if it meets the minimum performance required by DOT. Grades of "B" and "A" represent higher levels of performance than the minimum required by DOT.

 

[Randy]

The numbers do represent relative tire life regardless of brand as they all have to develop their numbers on the same government designated test course...

In an ideal world, perhaps. However, in actual practice and according to a number of people, including my own personal experience, as well as that of a number of entities that might even be considered authorities, they are only useful to compare tires within a manufacturer's tires.

For instance, to quote the TireRack web site http://www.tirerack.com/tires/tiretech/general/utqg.jsp :

"The problem with UTQG Treadwear Grades is that they are open to some interpretation on the part of the tire manufacturer because they are assigned after the tire has only experienced a little treadwear as it runs the 7,200 miles. This means that the tire manufacturers need to extrapolate their raw wear data when they are assigning Treadwear Grades, and that their grades can to some extent reflect how conservative or optimistic their marketing department is. Typically, comparing the Treadwear Grades of tire lines within a single brand is somewhat helpful, while attempting to compare the grades between different brands is not as helpful."

To quote a different web site:

"The treadware numbers on the sides of tires are DIFFERENT from manufacturer to manufacturer...so for the most part you can toss them out the window. Now you can reasonable hope to assume that a 300 treadware will last longer than a 100. On the other hand, the tires I have now have a 300 treadware and a 45,000 mile warrenty, while the goodyears i took off had a 420 treadware and a 40,000 mile warrenty. So much for nice easy comparisons...the only time you can use treadware ratings is within one companys own tire line (like Dunlops SP4000 vs SP9000, or etc)"

And, as you would expect, the temperature and traction ratings are similarly open to interpretation.

Hence, the reason I posted that which you chose to contradict...

 

[Ron]

The beauty of web information. There is a lot of it and it's all open to interpretation.

While I suppose I did contradict you a bit, I really meant to highlight the fact that there is a standardized government designated test that all manufacturers must perform that form the basis of these numbers. They are not just empty manufacturer claims based on each company's whim.

In my opinion, (and the Fed's apparently) extrapolating 7,200 miles of usage should give someone a solid mathematical basis to represent the ultimate treadlife of a particular tire. I'm sure manufacturers that produce low mileage tires claim the numbers are meaningless and high mileage tire manufacturers probably say that they're very meaningful. Logic indicates to me that unless boldface lying is going on, they do represent an accurate enough indication to impact the buying decision.

Treadwear warranties on the other hand are pure marketing. Decide on the mileage you want to claim, calculate the anticipated exposure, and add that to the cost of the tire. I agree with you that mileage warranty claims provide little indication of tire life and have no correlation to tearwear numbers. Saying though as your quote above did, that because one company claims a higher warranty mileage on a lower treadwear numbered tire than another does with a higher treadwear number in no way impunes the validity of the treadwear number. That's just pure and simple marketing.

But it's all for fun anyway.... Thanks for the banter Randy!

 

[Randy]

The beauty of web information. There is a lot of it and it's all open to interpretation.
[...]
But it's all for fun anyway.... Thanks for the banter Randy!

Exactly. Thanks right back atcha...

 

[Bonkers]

Well being the math lover that I am I was trying to cost analize a different set. If I'm going to loose 5,000 miles of distance it would take about 15 years before I saw a profit with the next set - assuming the prices remained the same. Of course its so much more difficult since the numbers aren't 100% to begin with.

Thanks again guys - I've got a much better idea now.