Uniform Tire Quality Grade numbers...

[Quattro Pete]

Yeah, treadwear index is not something you can truly rely on. There are just too many variables making a direct translation to a number of miles impossible. For one, treadwear index is not comparable across different brands, but only across different tire models of the same manufacturer. And then, all the other stuff like driving patterns, air pressure, vehicle weight, tire size, rotation frequency, ambient temperatures, pavement composition, and a bunch of others come to play.

 

[jsharp]

Looking around today, I found this same jewel of information "treadwear index is not comparable across different brands, but only across different tire models of the same manufacturer" that you mentioned

Well, that certainly helps explain why the numbers seem almost meaningless.

Because they are. The uniform part of the grading system was an obvious joke played on the consumer...

 

[jsharp]

Has anyone else noticed the Uniform Tire Quality Grade numbers for treadwear seem to be almost useless for determining how long a tire will wear?

I've had 3 sets of tires now on one vehicle, all different brands.

The first set with a treadwear number of 420 lasted over 40K miles.

Next set, treadwear rating 220 went a little over 30K miles.

The current set, treadwear rating 320 are looking pretty worn with less that 15K miles. I really doubt I'll get 25K miles from them.

I'm wondering what exactly the numbers were good for...

 

[Quattro Pete]

Well, that's the puzzling point. There is supposed to be a "reference tire" with a treadwear index of 100 to which all others are compared. However, it is not clearly stated whether there is just one government-provided reference tire or whether each tire manufacturer has their own reference tire.

http://www.safercars.gov/Tires/pages/TireRatTreadwear.htm

But I agree, this index isn't very helpful. In Europe, it is not used at all, probably because they decided it holds no value. Tire manufacturers still print it on the tires in Europe (so that they comply with DOT just in case these tires were to be shipped to North America), but you won't find any mention of it in any of their literature or on their websites.

 

[jsharp]

Here's another link with the same info, but possibly a little more -

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=48

It's also unclear to me where this "reference tire" comes from. I have a feeling the manufacturer provides their own which would make it a lot less objective

Oh well. The gov missed an excellent chance to actually provide useful information for the consumer. Right now we have all the regulation, but none of the benefits...

 

[ccs2k1]

The only time the treadwear number is somewhat useful is when comparing tires within the same brand. Cross brand comparisons are useless. If available, the best indicator would be the treadlife warranty, but once you get in UHP and max performance segments, most manufacturers won't offer warranties.

 

[CapriRacer]

FYI,

There IS a reference tire and it's known as the SRTT - Standard Reference Traction Tire. It's the same tire used by the industry for traction testing comparison. This tire is used because there already was a need to have a standard tire for traction testing - no sense having 2 reference tires.

The UTQG test for treadwear is highly variable - it's only a 10,000 mile test. So small difference get magnified.

But the "klinker" is that the regulation doesn't say that all the tires have to be tested - just that the manufacturer has to be able to trace their rating to the test. This may mean the connection may be quite distant.

Also, the rating isn't the result of the test. The results are used to set the rating. Some manufacturers like to be conservative and some are quite aggressive with the rating. So some folks think this means you CAN'T compare ratings between manufacturers - but I think it's a lot more complicated than that.

HOWEVER, the physics of tire wear is such that the actual wear rate is more dependent on how much cornering you do (and how hard you corner), rather than how many miles you put on. This is one of the reasons the tire industry fought against the ratings - but many consumer groups pressured the Feds to institute the rating system in spite of its shortcomings.

Some folks think tread wear warranties are a good indicator - and this is somewhat true - but tread wear warranties are difficult to qualify for - alignments, rotations have to be followed religiously - so there is very little warranty claims made for tread wear. This makes the warranty ratings suspect as well.

Hope this helps.

 

[Gary Allan]

quote:

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Also, the rating isn't the result of the test. The results are used to set the rating. Some manufacturers like to be conservative and some are quite aggressive with the rating. So some folks think this means you CAN'T compare ratings between manufacturers - but I think it's a lot more complicated than that.

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This was how it was explained to me. Basically the cheaper the tire ..the closer they were to the true number of the rating. The more expensive brands (premier brandnames) would under rate their tires.

I agree that it's mostly worthless.