[Tireman9]

To CWtheMan
Answering your comments/questions:
"They didn't have a tire problem. They followed the standards instructions. The tire industry had the problem by allowing tires without any load capacity reserves to be used as OEM on RV trailers."
Well CW, as you know it is the responsibility of the vehicle MFG to select the tires and to specify the necessary inflation needed to support the GAWR. The Regulations do not say "Carry the GAWR plus bit more"

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"(IMO the tire manufacturer's are using a different formula. What else would explain the ST tire industry-wide speed ratings going to as high as 87 MPH? Is NHTSA looking the other way?"
The formula has not changed. The proof of that can be confirmed simply by looking at the Load/Infl tables from the '70s and comparing with the current tables.
The Speed ratings were added, almost overnight, to address Federal Trade Commission, not DOT rules on tariffs on non-speed tires vs speed rated tires. Given the stated 1 year warranty some might think that since it is possible for a tire to run to a higher than 65 mph speed for a few hundred or even a couple of thousand miles some might have decided to play the odds. NHTSA simply requires tires to be capable of passing certain well-defined tests and uses the Tire Industry published Load & Inflation tables when setting the test conditions.

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"(Carlisle CEO told Modern Tire in an interview that ST tires use larger & stronger cording. Do you have information that makes that untrue?)" Since it is the air pressure that supports the load, not the tire structure the "strength" of the body cord is not an issue.
Body construction strength can be achieved using a number of different materials and for each material, cords are made in dozens of different configurations. Even the number of "cords per inch" can be adjusted such that fewer cords of larger or stronger material can be substituted for more cords that are smaller or not as strong. So it's entirely possible to have larger and stronger cords yet end up with a weaker sidewall. So the statement can be true but is not a requirement for ST type tires. Think for a moment of using smaller and fewer steel cords vs larger and more polyester. So which is "Better"?
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Having designed Indy type, Truck, LT, P-type and even Temporary spares I see no limit in the designs to what materials could be used. In my career, I have used and evaluated Nylon, Polyester, Steel, Rayon and Fiberglass in numerous levels of size and strength. While each may have a balance of cost vs performance that pushes the design engineer to select one combination over another. BUT as I said if just using "larger & stronger cording" somehow allowed a tire to carry 20% more load why wouldn't a company increase the load capacity of their LT tires to beat the competition?

I read the Triangle USA warranty. Sounds fine to me, so why don't we see lots of RV trailers sold with Triangle brand? I have no idea.

You may not know that Goodyear was the company that introduced the ST type tire, over the objections of other tire companies in US Tire & Rim Association according to a contact I have in the tire industry.

RE why other major tire companies don't make ST type? We can only guess but I don't see the cost of making the tires as the reason.