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Old 10-25-2013, 10:46 AM   #1
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New Info on max speed of Marathon tires

Finally chased down the answer to the question of max speed rating of GY Marathon St type tires.
Getting to the bottom was a challenge because I ran into "customer service" people who could read from a script but had no idea why they were giving me the answer they were.

Even got to the engineers at Tire & Rim Association and based on their answers it was obvious they had not thought about ST type tires or the unique nature of RV application so acted a little surprised when I identified the engineering analysis that indicated that the current loads are too high for many trailers and that the load capacity should be decreased by 15% or more.

Anyway here is the bottom line.

For Goodyear Marathon tires only:
There is a Tech bulletin PSB#2011-13 that uses information from TRA (blind leading the unknowing in my opinion but they are the ones that have to stand behind their warranty).
The tech bulletin says that the normal max speed for Marathon ST type tires is 65 mph. This speed can be increased up to 75 only if the inflation pressure is increased by 10 psi.
Goodyear does not support or condone operation above 75 at any time.
The trailer owner is responsible to confirm the rim is rated for the new inflation level.
While TRA indicates a further increase in speed might be achieved Goodyear has decided not to adopt this option.

The person I talked with at Tire Rack said they had already changed their web site to indicate this applied to Goodyear tires only and that they were attempting to learn if any other ST tire manufacturers were willing to make a similar change. As of Saturday Oct 19 they had not identified any other tire manufacturer willing to make such a change.

Example:
If you have a GY Marathon ST225/75R15 LR-D it is rated for 2540# @ 65psi and a max speed of 65 mph. If you increase the cold inflation to 75psi the tire would now be rated for 2540# @ 75psi and a max speed of 75 mph.
The example currently only is OK for Goodyear Marathon ST tires as I have not seen a published document from any other tire manufacturer.
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Old 10-25-2013, 12:07 PM   #2
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Here's what others have said about this;
http://www.airforums.com/forums/f438...ure-52696.html
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Old 10-25-2013, 01:53 PM   #3
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Question

And the rational for towing @ 75mph is.......?


Are we there yet?

Bob
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Old 10-25-2013, 02:40 PM   #4
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Originally Posted by ROBERT CROSS View Post
And the rational for towing @ 75mph is.......?


Are we there yet?

Bob
Good question Bob.
I know for me, it is taking some time getting use to a slow pace of retirement. My whole life, I've been into speed one way or another. Everything I've had on wheels or in the water I've taken apart and put back together for more HP. So YES! it is important for me to have tires I can count on. I'm really trying to slow down to 60 - 65 mph, but my brain keeps telling the foot to not let that truck go by! Man some of them do book it down the road. I'll get there some day
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Old 10-25-2013, 03:08 PM   #5
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Quote:
Originally Posted by RLS View Post
Good question Bob.
I know for me, it is taking some time getting use to a slow pace of retirement. My whole life, I've been into speed one way or another. Everything I've had on wheels or in the water I've taken apart and put back together for more HP. So YES! it is important for me to have tires I can count on. I'm really trying to slow down to 60 - 65 mph, but my brain keeps telling the foot to not let that truck go by! Man some of them do book it down the road. I'll get there some day
Thats why I have the Allison.....no tires to worry about.

My pal Todd...

Bob
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