UTQG Temperature Ratings - What's the Difference

['05 Outback 2.5i]

Okay, first I understand the basics of the UTQG ratings for traction, temperature and tread wear rating, but I must admit to being baffled by some combinations of the numbers. The tire in question is the much talked about Yokohama A/T-S. Most people seem to be running them in the 215/65-16 size which has a Traction rating of 'A' as well as a Temperature rating of 'A' along with an 'H' speed rating.

Now if you look at the 235/60-16 size of the same tire, it carries the same speed rating, treadwear rating, and traction rating, but drops to a 'B' temperature rating, and I have to wonder why, and if it is really a concern (Particularly if the tire is able to earn an 'H' speed rating).

Anyone have some thoughts to clarify this?

[TeamFCAR]

Scott,

At the risk of getting it wrong, I would suggest you go to the TireRack.com and read their explanations.

To explain your specific question, a wider tire may have a harder time transferring the heat for the Temp rating (affects load rating) and the wider tire may not clear water as well and knock the Traction value.

There is so much that goes into tire design I am sure there is more to it than my brief response.

I hope you get a better reply, but I still think you're better off going to a respected source like the Tire Rack or Discount Tire (possibly a site sponsor).

Mike

['05 Outback 2.5i]

Hey Mike,

Thanks for your response. I have done some online research, including vendors like tire rack (who's FAQ on the subject I linked in the first post). Unfortunately it doesn't really provide much insight into my question. While I don't think width is a contributing factor (high performance cars run much wider tires with 'A' temperature ratings, I do wonder if it is something to do with the load rating being higher and the fact that the tire is tested at maximum load?

I'm sure I'm over thinking this, as I tend to do with most things, but it would be nice to know..

[Seabass]

I wouldn't think that the wider tire would have enough of a different contact patch to increase temps enough to effect that. Very strange. Have you compared that to the manufacturers website? I'd be curious if that was a typo. Any extra heat from more rubber hitting the road would probably be negated by the additional surface area to dissipate heat. Unless that particular tire has a slightly different structure in the different size.

The temp ratings seem very erratic for that particular tire on tire rack. If you look at the specs for all sizes, it seems there are a few scattered A rated sizes at random. Some of them are 255 and some are 215. Seems like bad info to me.

[TeamFCAR]

Scott,

It is hard not to over think tires, the are in fact "where the rubber hits the road", and there are so many factors involved.
Most of my experience is with racing slicks and "Rain" tires but on a general level "tires are tires". As you mention wider tires can have an A rating but the carcass had to be engineered to help with that. If you start with a standard construction for the tire you mentioned earlier, 215/65-16 size, then use the same construction on a wider version, the added width will hinder the cooling of the tire.
In Formula 1 for the last few years the top teams have been experimenting with CFC gases and CO2 to better transfer the heat from the tread to the rim and thus gain an advantage in performance.
For the load rating, tire pressure is a big factor. This is often overlooked when new tires are installed that are of a different make and model from the original. Aside from the goal of the OEM to use lower air pressure to get a better ride or increase pressure to get better mileage, using a tire with a higher load range will offset the base pressure needed for even wear.
So now I've gotten deeper into this than I had intended and hope the list has either ignored this thread or at least not fallen asleep.

I hope this is of help,

Mike

['05 Outback 2.5i]

Originally Posted by Seabass

Have you compared that to the manufacturers website? I'd be curious if that was a typo.

Okay, I feel like an idiot, Yokohama's Website lists that tire with an 'A' Temperature rating, not a 'B' as the Tire Rack Spec Page does...

Well, I feel better about the idea of running the 235/60 now anyway..

[Seabass]

...after looking at the yokohama website, it looks like it has to do with side profile. Almost all of the tires with 65 or lower (except those with 275 widths or higher) have the A temp rating. So it likely has something to do with heat production and dissipation.

['05 Outback 2.5i]

Originally Posted by Seabass

I wouldn't think that the wider tire would have enough of a different contact patch to increase temps enough to effect that. Very strange. Have you compared that to the manufacturers website? I'd be curious if that was a typo. Any extra heat from more rubber hitting the road would probably be negated by the additional surface area to dissipate heat. Unless that particular tire has a slightly different structure in the different size.

The temp ratings seem very erratic for that particular tire on tire rack. If you look at the specs for all sizes, it seems there are a few scattered A rated sizes at random. Some of them are 255 and some are 215. Seems like bad info to me.

For anyone following this, I had contacted TireRack, and they pulled a tire from inventory and checked what was stamped on the sidewall, sure enough, the 235/60-16 carries an 'A' temperature rating, and not the 'B' that the Tirerack's website had shown.

Tire Rack sent me an e-mail saying they would be updating the site..

Originally Posted by Seabass

...after looking at the yokohama website, it looks like it has to do with side profile. Almost all of the tires with 65 or lower (except those with 275 widths or higher) have the A temp rating. So it likely has something to do with heat production and dissipation.

That makes more sense to me..

[OutdoorOBW]

Now to completely derail this thread:

Outback2.5i are you planning on getting a set of 235/60/16 A/T-S'? If you are do you have any info on if they will rub at all, lower MPG or anything?

['05 Outback 2.5i]

Originally Posted by OutdoorOBW

Now to completely derail this thread:

Outback2.5i are you planning on getting a set of 235/60/16 A/T-S'? If you are do you have any info on if they will rub at all, lower MPG or anything?

If I stay with 16" wheels I most likely will go with the 235/60-16 Yoko A/T-S. I haven't found anyone specifically running them yet, but forum member 'Bimmer' is running 235/55-17 Eagle GT's on his Outback and reports no rubbing issues. The specs for the Eagle GT tire show a wider section width than the Yoko A/T-S (9.7" vs. 9.4"), and a slightly taller profile (27.2" vs. the Yokos 27.0") so I'm inclined to think there will be no rubbing issues...

Of course, I'm also considering moving up to 17" wheels (primarily because I'd like to upgrade the brakes to the LGT rotor size and calipers) in which case I'm torn between trying the 235/55-17 Eagle GT's or rolling the dice on the more rugged A/T-S in the 225/60-17 size and seeing if they fit (they are 27.6" tall so they might be a problem, because I'm not sure I want to go to the narrower 215/60-17 tire) ..

As for MPG, I'm sure there will be a hit, the tires by design have a higher rolling resistance, and adding section/tread width only increases that. The slightly taller profile will also mean taller overall gearing, and some loss of 'pep' when accelerating, something I'd worry about more if I had an automatic, but I'm not terribly concerned about either, your views may be different though..

P.S. -- Tire rack updated the UTQG information for the tire..