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Old 04-16-2009, 07:26 PM   #15
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Towing speed

First I apologize to the two experienced folk who posted this above. It is a common misconception that all ST tires are limited to 65 MPH. Not so. They are only limited to 65 MPH at the "normal" PSI for the load you are carrying. If you go to the Goodyear Marathon specs page on line, you'll find a PDf file that specifically states that towing at speeds between 66 and 75 MPH requires increasing the PSI to 10 PSI over whatever the top number listed on the tire sidewall. Obviously, this also requires that the wheel be rated for the increased pressure. For example, the STs on my TT are rated for X number of lbs. of load at 65 PSI. At that "normal" pressure, the industry standard for ST tires is 65 MPH. HOWEVER, if the pressure is increased to 75 PSI, the tire is rated for towing 66-75 MPH.

So, just flatly stating (without qualifiers) that all ST tires can't go above 65 MPH is not a completely true statement. At the pressure listed for max load as on the sidewall, it's true. But if the pressure is increased, it is not true. These numbers are not specific to Goodyears but are the standards to which ST tires must be built. This info applies to all STs sold in the US. The Goodyear page also warns not to go over 10 PSI above the "normal" setting. I have found this same information buried in the fine print at the bottom of load/PSI charts for a couple of other brands besides Goodyear. My TT wheels are stamped "75 PSI max." The sidewall PSI for max load is 65 PSI. Because I cruise at 67-68, I run my STs at 70 PSI.

This standard isn't all that different than other tires. My load range E LT tires list a sidewall PSI of 80 PSI for a given weight. However, the load chart notes that in hot weather or if going fast, the PSI can be increased up to 10 PSI over the PSI listed on the sidewall of the tire. In the summer, I run my truck tires at 85 PSI. Also, note that for either the STs or LT tires, increasing the PSI will never increase the load carrying capacity. The extra pressure just allows a little extra stiffness in the sidewalls so the flexing (which causes heat) is kept tolerable. It allows the tires to run cooler at higher speeds.

I am not recommending any particular speed for the OP. So much depends on terrain, equipment, experience, physical condition (tired?) etc., etc. I'm just trying to stop the old info that STs can't go above 65 MPH. Sorry for the length.
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Old 04-17-2009, 11:54 AM   #16
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As a point of interest, last trip out, with our rig (ST tires on the trailer) I checked the side wall temsp at a stop. The weather was about 80 dF and we had been running 65 mph for a couple of hours.

Truck front...105 dF
Truck rear....100 dF
All trailer tires...95 dF.

Plan to keep checking them as the weather gets warmer.

Ken
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Old 04-17-2009, 12:07 PM   #17
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Quote:
Originally Posted by ATVr View Post
First I apologize to the two experienced folk who posted this above. It is a common misconception that all ST tires are limited to 65 MPH. Not so.
Dueling sources. Check HERE.

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Old 04-17-2009, 01:57 PM   #18
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I must respectfully disagree that the sources are "duelling." What you posted is not wrong and does not conflict with the LT industry standards. ST tires are rated at 65 MPH. But, that is not a complete statement. They are limited to 65 MPH ONLY when inflated to the number on the sidewall for maximum load. The rest of the story is that the STs can be inflated to 10 PSI over the sidewall pressure and then you can pull at 66-75 MPH. This does not conflict with your Discount Tire data. It only qualifies it. This all assumes the wheels are rated for that PSI. Also, as I noted before, it is not just Goodyear that says this. Tires of all kinds sold in the US are supposed to be built to promolgated industry standards for the given class of tire. As I stated before, I have seen the same "10 PSI" stuff in fine print at the bottom of load/psi charts for a couple of other brands. This was at the tire store... I can't find examples of other brands on line. But, Goodyear makes a lot of ST tires, so I would trust their web page.

I found the source in about 5 places, but it's always PDF which won't allow copying. So, I have retyped part:

"March 27, 2006

SUBJECT: Marathon Special Trailer Applications - General Information

This information is designed to help you obtain the best performance from tires with the ST (Special Trailer) designation. Please review the following important points with your Goodyear Marathon customers.

Industry standards dictate that tires with the ST designation are speed restricted to 65 MPH under normal inflation and load conditions unless a different speed restriction is indicated on the sidewall of the tire.

Based on industry standards, if tires with the ST designation are used at speeds between 66 and 75 mph, it is necessary to increase cold inflation pressures by 10 psi above the recommended pressure for the load.

Do not exceed the maximum pressure for the wheel.
If the maximum pressure for the wheel prohibits the increase of air pressure, then the maximum speed must be restricted to 65 mph.
The cold inflation pressure must not exceed 10 psi beyond the inflation specified for the maximum load of the tire."

The letter goes on with more warnings like the extra inflation does not increase the load carrying capacity and you shouldn't drive off cliffs. I don't advocate pulling at 75, but you could, as far as the tires go. Camping weather coming!! yeehaw.
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Old 04-19-2009, 08:13 AM   #19
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There is valuable info contained in this thread. I, personally, tow between 62-65mph because that is my confort zone w/ 14K behind me. That is fast enough that I don't feel like a hazard to others.

VRacer,
Amen to that. GM is losing a part of the market by not offering a 4.10-4.30 gear. If you tow over 16K, you will need a Ford.
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Old 04-19-2009, 09:44 AM   #20
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Originally Posted by evan0810 View Post
If you tow over 16K, you will need a Ford.
Not to start a brand war, but the following is from the press release for the new 2010 heavy duty Dodge/Cummins trucks that are about to be released:

Quote:
A trailer brake controller is built in. Capacities are up, with Ram 3500 with dual rear wheels, diesel, automatic, and 4.10:1 rear axle sporting a 25,400 pound combined gross weight rating; the 4x4 diesels get an increased front axle weight of 5,500 pounds (for better front weight capabilities including heavier snow plows); and the Ram 3500 can tow 18,500 lb, with a maximum payload of 5,100 pounds.


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Old 04-20-2009, 04:38 PM   #21
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On semi-flat roads at highway speeds of about 58-59 I get anywhere from 12-13 MPG. The tech stays at about 1900 RPM's and might bounce up to 2200 if I'm going against the wind. I put a new set of tires on the trailer last week. This past weekend going camping westward I got 13.1 miles per gallon. My old tires had a "Max" tire pressure of 45 PSI. The new ones are "Max'ed" 50 PSI. He said you can keep them at 50. Maybe that is why I got over 13 MPG. Actually I'm happy on anything over 12.....
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Old 07-21-2009, 01:38 PM   #22
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There is some good advise in the above posts. I believe that traveling an Interstate at 45 mph would be more of a hazard than traveling at 70 m.p.h. Having said that the best advise I can give is, "find a speed you feel comfortable at, then slow down 5 m.p.h. "

45 is not only too slow but illegal in most states. For example, the minimum legal freeway speed in Michigan is 55mph.

There are trailer tires that are designed for speeds up to 100mph.
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