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Old 01-06-2006, 09:15 AM   #1
Porter
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Have a Nice Day? Goodyear Assurance... hmm...

My folks "surprised" me by replacing the worn OEM Michelins on the Acura 3.2TL I'm driving with a set of Goodyear Assurance TripleTreds when I was out of town skiing for the weekend in another vehicle.

Steering response is abysmal. I'm sure this is largely due to the ~30psi that tire shops seem to like to put in tires nowadays, but really... it's like the steering rack is missing a few teeth.

If they're anything like the RE950, they'll do well with pressures at or approaching the target max load rated pressure. I'll air them up tonight to 44f/42r and post the results. If they aren't improved, I'll probably head down to the shop where they bought these and have them swapped out for something else.






<rant>

By the way, the way Tire Rack divides up their tire "classes" really irritates me. It's completely arbitrary and has nothing to do with actual tire performance. As far as I can tell, the different classes of tire are only determined by available sizes and speed ratings, which really have nothing to do with on-road tire performance.

It sure would be nice to see a comparison between equivalent technology levels between brands. For example, Bridgestone RE950 vs. Goodyear Assurance Tripletred vs. Kumho ASX... all of which are available in common sizes like 225/50R16 and have similar tread design (and target market) approaches. On the other hand, I suspect a direct comparison between the "Passenger All-Season" Assurance and the "High Performance All-Season" Eagle GT-HR (both by Goodyear) would net very interesting results, especially considering the price difference between the two products and their rather curious positioning in the Tire Rack lineup.

The HP-AS, AS, and UHP-AS designations mean nothing in terms of real-world tire behavior, and only seem to serve to divide the tire list into sections in which certain tires perform well against their "competitors" and avoid being compared against some other tires. You can look at the tires included in the "bottom" of each category for evidence of that. I mean come on, you can look at the tread design of an H rated Goodyear Assurance TripleTred ($120+) and know that it shouldn't be compared in the same category with an S rated Bridgestone BT70s ($60). It's disingenuous.

Let's see some comparisons between similarly engineered products, please!

</rant>
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Old 01-06-2006, 10:33 AM   #2
subieworx
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I would agree that many of the designations seem to a marketing ploy.
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Old 01-06-2006, 12:52 PM   #3
Uncle Scotty
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Quote:
Originally Posted by subieworx
I would agree that many of the designations seem to a marketing ploy.

....and purposefully, confusingly, misleading, as seen in threads here constantly.
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Old 01-06-2006, 05:10 PM   #4
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we do not divide the tires into catagories ... the manufacturers decide where the tires are targeted .... and maximum tire load capacity is achieved @ 36 psi .... going up to 42 or 44 PSI does not offer any more load capacity
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Old 01-07-2006, 08:19 AM   #5
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Quote:
Originally Posted by Luke@tirerack
we do not divide the tires into catagories ... the manufacturers decide where the tires are targeted .... and maximum tire load capacity is achieved @ 36 psi .... going up to 42 or 44 PSI does not offer any more load capacity
Maybe I'm misunderstanding something... when the tire indicates "MAX LOAD xxxxLBS AT 44PSI" I take that to mean that the tire reaches its maximum load capacity at 44psi. That seems borne out by various manufacturer literature I have seen and a conversation with a tire engineer at the Michelin proving grounds in Laurens, SC.

Certainly going from 32psi to 44psi will stiffen the sidewalls, hopefully taming some of the vagueness in the steering response. My several sets of Bridgestone RE950s (also a 44psi tire) in various sizes operated best in all conditions in the 40-44psi range.

You're saying that the max load capacity is actually achieved at 36psi, a number that is not indicated anywhere on the tire. How do you determine that?

Thoughts?
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Old 01-07-2006, 10:01 AM   #6
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P-metric tires reach their max load capacity @ 35psi
Euro-metric tires reach their max load capacity @ 36psi
XL-rated Euro-metric tires reach their max load capacity @ 42psi

http://www.tirerack.com/tires/tirete....jsp?techid=21

http://www.toyojapan.com/tires/pdf/TTT_18.pdf

http://www.toyojapan.com/tires/pdf/TTT_17.pdf
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Old 01-07-2006, 10:52 AM   #7
Porter
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Interesting. So the indication MAX LOAD XXXXLBS AT XXPSI printed on the tire is just put there to confuse and mislead the consumer?

How clever.

Somehow, I think the likelihood of the assertion that all P-metric tires in all sizes from all manufacturers reach their engineered max load capacity at 35psi is, shall we say, pretty weak.


The basic physics of a pneumatic toroid contradict your assertion, especially in cases of very low-profile tires. They naturally require higher inflation pressures to maintain their shape when loaded due to lower air volume compared to cross sectional area. That's one of the reasons why many low-profile tires have a max load rating pressure of 51psi.

Last edited by Porter; 01-07-2006 at 11:05 AM.
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Old 01-07-2006, 02:02 PM   #8
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Quote:
Originally Posted by Porter
Interesting. So the indication MAX LOAD XXXXLBS AT XXPSI printed on the tire is just put there to confuse and mislead the consumer?

How clever.

Somehow, I think the likelihood of the assertion that all P-metric tires in all sizes from all manufacturers reach their engineered max load capacity at 35psi is, shall we say, pretty weak.

The basic physics of a pneumatic toroid contradict your assertion, especially in cases of very low-profile tires. They naturally require higher inflation pressures to maintain their shape when loaded due to lower air volume compared to cross sectional area. That's one of the reasons why many low-profile tires have a max load rating pressure of 51psi. [emphasis added]
While I agree with what you're saying, Porter, you're pissing up the wrong tree (for the 2nd time in this thread). First you bitch at Tire Rack for improperly classifying tires, when in fact it's the manufacturers who classify their own tires. I think Tire Rack goes well above and beyond what any other tire vendor does when it comes to actually testing various tires to show what their performance potential actually is, not just what the manufacturers say it is.

Now you're getting bitchy with ripvw. Maybe that wasn't your intention, but that's the way I read it. It's not his (ripvw's) assertion, it's the tire manufacturers' assertion. The load ratings are defined by an industry standard, not ripvw's post on the NASIOC forum.

Seems a little silly to get so worked up over it. Inflate your tires to what you think feels good/performs best and move on.

Pat Olsen
'97 Legacy 2.5GT sedan
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Old 01-07-2006, 06:39 PM   #9
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I'm not trying to be bitchy. I'm just interested in seeing intelligent comparisons between products.

Tire Rack is a great company, and Luke has gone way above and beyond to support and assist this community. I'm just frustrated by the fact that they have a huge amount of tire data but don't structure their website in a way that allows rational comparisons between products. It's their web site, not the manufacturers'.

Again, not trying to crawl up anybody's rear end over it, I'm just frustrated by what I perceive as a lack of accurate information. The "all tires achieve maximum load rating at 35psi" bit is just one good example of that.
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Old 01-07-2006, 07:43 PM   #10
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Quote:
Originally Posted by Porter
,,,I'm just frustrated by what I perceive as a lack of accurate information. The "all tires achieve maximum load rating at 35psi" bit is just one good example of that.
as I stated above, there are several different max load ratings depending upon whether the tire is a P-metric, Euro-metric, or XL-rated of either type. here is another bit of "inaccurate" information from Bridgestone:

"Euro-Metric
This system originated in Europe and is also referred to as the European Metric System. Most European tire manufacturers build tires that conform to this system. The Metric System is very similar to the P-Metric System, except in terms of load carrying capacity. Load carrying capacities of Metric and P-Metric tires are sometimes not the same, even for two tires of the same size designation.

...another load related difference between P-Metric and Metric sizes is the maximum inflation pressure. P-Metric standard load tires have a maximum inflation of 35psi (pounds per square inch) while Metric are 36psi. Some speed rated tires have a maximum inflation of 44psi, this capability has been added to enhance handling and high speed capability in some vehicles..."

from this link:

http://www.tiresafety.com/passenger.asp

in addition, as I'm sure you're aware, optimum tire pressure is a tradeoff between steering feel and max grip. Increasing tire pressure beyond 40psi cold will likely enhance steering feel at the expense of grip. anything below 35 to 36psi cold is most definitely going to reduce grip since the tire does not have sufficient pressure to reach its maximum load, hence the sidewalls are not sufficiently stiff to provide maximum contact patch width during hard cornering. it is, afterall, the width of the dynamic contact patch that determines dry grip.

I have found that most high performance tires achieve max grip on the street between 36psi and 40psi cold - my experience is with Pirelli, Goodyear, Michelin and now Falken summer tires. It is my belief that many on this board run higher than optimal pressures due to their reliance on steering feel as the sole determination as to what constitutes proper pressure. indeed, it is an issue even for professional drivers, who often haggle with the team engineer over tire pressure settings for the same reason. a little more pressure "feels better", while testing has shown that a little less actually provides more grip and faster cornering speeds.

in any case, Goodyear definitely does not consider the Assurance model a performance tire - that much is clear from their own website. Based on your feedback regarding the tires, I say go with your initial gut reaction to them and trade them in on something better.
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Old 01-08-2006, 06:52 PM   #11
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Thank you. That was an intelligent and insightful post.
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Old 01-09-2006, 09:13 AM   #12
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great info. thanx
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