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Old 02-12-2012, 04:54 PM   #85
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Originally Posted by Phil&Sher View Post
I read somewhere that ST trailer tires are rated for 65 MPH and LT truck tires are rated for 95 MPH. I also read a post on another forum from a guy who was having lots of tire problems on a heavy fifth-wheel, even though he was cautious about his weight and speed. He switched to from 15" ST's to 16" LT's and his problems disappeared.

ST Goodyear Marathons are speed rated R = 106mph
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Old 02-12-2012, 05:33 PM   #86
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This article posted on Discount Tire's website disagrees with a speed rating of 106 mph: Trailer Tire Facts - Discount Tire

Actually my understanding is that ST tires are not required to be speed rated at all. The recommendation is that speed not exceed 65 if you inflate them at 65 psi. Goodyear has stated on its website that you can increase both inflation and speed to 75: http://www.tirerack.com/images/tires...plications.pdf . Any manufacturer may do the tests for speed rating if it wishes. In another place on the Goodyear website, it states the ST speed rating is 65.

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Old 02-12-2012, 05:40 PM   #87
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Maybe that was KPH.
65 MPH = 104.6 KPH which is very close.
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Old 02-12-2012, 05:56 PM   #88
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Quote:
Originally Posted by tvanwave View Post
ST Goodyear Marathons are speed rated R = 106mph
Good Luck
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Old 02-12-2012, 07:13 PM   #89
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My understanding is that the trailer tires are not rated but passenger tires are.
The Goodyear marathon has a max speed rating of 65 MPH. If your inflation for your trailer weight is below the max pressure rating of the tire then if you inflate ten pounds over that pressure you can increase max speed by 10.
Go to Goodyear website and confirm this for your self.
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Old 02-12-2012, 07:14 PM   #90
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Goodyear Product Service Bulletin #2011-13
May 18, 2011

TO: Goodyear Company Owned Outlets, Goodyear Contract Dealers,
Goodyear Canada Inc. Dealers

Subject: Tires for Trailer Use Only: General Information (replaces PSB 2006-06)


This bulletin provides important information to help your customers obtain the best performance from "Special Trailer" tires. Please review the following important points with your trailer tire customers.
Special Trailer ("ST") Tires
Goodyear Marathon trailer tires are widely used in a variety of towable trailer applications and are designed and branded as "ST" (Special Trailer) tires.

• Industry standards dictate that tires with the ST designation are speed rated at 65 MPH (104 km/h) under normal inflation and load conditions.
• Based on these industry standards, if tires with the ST designation are used at speeds between 66 and 75 mph (106 km/h and 121 km/h), it is necessary to increase the cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.

o Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load carrying capacity.
o Do not exceed the maximum pressure for the wheel.
o If the maximum pressure for the wheel prohibits the increase of air pressure, then the maximum speed must be restricted to 65 mph (104 km/h).
o The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire.
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Old 02-14-2012, 05:54 AM   #91
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At this point in the GM st tire discussion and other st tire discussions , does a speed rating have any believable relevance? I think not.
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Old 02-14-2012, 11:05 AM   #92
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Originally Posted by Kosm1o View Post
At this point in the GM st tire discussion and other st tire discussions , does a speed rating have any believable relevance? I think not.
Yeh, if the tread comes off at 65 or a 106, what's the difference?

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Old 02-14-2012, 05:13 PM   #93
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Quote:
Originally Posted by azflycaster View Post
Maybe that was KPH.
65 MPH = 104.6 KPH which is very close.
I recant - I cannot find the website the info came from, so I admit my mistake. Glad to be corrected though!!
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Old 02-22-2012, 11:37 PM   #94
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ST tires

A couple of years ago I posted extensively on the Tires ...Tires...Tires blog and was hammered. I actually talked with the Engineer responsible for tire testing who was employed by the National Highway Transportation Safety Administration. His advice was to obtain a tire with highest speed rating because THE SPEED RATING WAS THE OVERALL ACID TEST OF HOW MUCH A TIRE COULD WITHSTAND BEFORE THE RUBBER COMPOUNDS LOST THEIR INTEGRITY WHICH ALLOWED THE BELTS TO SLIP AND THE TIRE TO FAIL. Simply put, if a tire carries a speed rating of 95 mph, then it can run (when properly inflated according to inflation/weight charts) all day long at 65 or even 70 or what ever speed you are brave enough (or stupid enough) to run at and stay together.
How much sence does it make to run a tire rated at 65 mph at 70 mph. The heat comes from the flexing of the sidewall and the contact with the hot road. Again, we have chosen to purchase the most durable recreation vehicles on the market, why chance damaging them with inadequate tires. The choice is ours, either slow down (to say 55 mph) or buy better tires. The yard stick of better tires is the speed rating.
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Old 02-23-2012, 06:31 AM   #95
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The same tire [LT] run on a pickup, or run on a trailer, is subject to different ratings by the manufacturer. Things are both a bit simpler and a touch more complicated than they appear.

There's a new thread on WOODALL's involving LT vs ST and has two tire engineers onboard making differentiations and clarifications; as linked in this post on AIR. Upsizing and watching ratings are "good", just how to determine what LT tire is workable now has some numbers attached to it.

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Old 02-23-2012, 09:06 AM   #96
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Originally Posted by REDNAX View Post
The same tire [LT] run on a pickup, or run on a trailer, is subject to different ratings by the manufacturer......
Hard to understand why, although I'm sure you're right about the different use ratings manufacturers might assign to the same tire. Common sense would make me think that the tire doesn't know what sort of vehicle it's mounted on. The tire just "knows" what conditions it's experiencing: speed, load, inflation pressure, and temperature.

Presuming proper inflation, 55mph on a cloudy, cool day at half rated load should beat 75mph on I-10 in August at max load, no matter what kind of vehicle it's mounted on.

For now, I'm running my Marathons at 65psi, half-max load in the trailer, 55-60mph, with tire pressure/temp monitoring, and hoping for the best.
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Old 02-23-2012, 11:14 AM   #97
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The tire just "knows" what conditions it's experiencing

Why it is worth reading the thread. The ratings have to do with the beatings the tire suffers. The ratings may not be perfect (more about wording, perhaps), but an understanding of how they are interpreted (supplied in thread) gives one better guidelines that just "go bigger and heavier" as inflation pressure lower than sidewall maximum is contraindicated. One needs to come closer -- and one can -- is the point.

12-15% load reserve plus max tire pressure is ideal (where the wheel is properly rated and is of correct rim width).

That's it in a nutshell.

But how to cross-reference LT against ST tires is where the devil is in the details. It is not a direct correlation due to use.

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Old 02-23-2012, 11:29 AM   #98
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For me, the discussion of LT versus ST tires is not really about ratings. ST tires would be great if each tire actually meets the ratings that they are given. But apparantly a much larger percentage of ST tires fail. I have several friends who have had GYM's fail while they were running TPI system and reading 65 psi when it went, and tires were 1 to 3 years old. My choice to go to LT tires is made knowing that they are not the best tire on paper and in spec ratings for the job. But in believing that they are better made and have a lower failure rate than the ST tires. Multiple axles on trailers can cause overloading issues on trailer tires that cars and trucks do not have. My understanding is that the ST tires are rated to allow for this, so I use a large safety factor for the LT tires. But if the ST tires are defective that seems to trump ratings. The tire engineer I know worked for GY, in China for a while, and he runs GY LT tires on his trailer.
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