"My 2012 Airstream Classic came with Goodyear Marathon ST225/75R15 LR-D tires. I would like to tell you how many original installed tire I have had blowout using the original and same size tires as replacements. I even replaced the LR-D's with LR-E's and still only get about 3,000 miles before blowouts. It is the damage caused by the blowouts that concerns me most. I am tired of fixing my trailer after blowouts.
As I alluded to in my earlier message, I owned an Alpha 5th wheel that had 16" wheels as the original size. After 5 blowouts in one 6,000 mile trip I replaced the tires with Michelin LT235/75R16 XPS RIB (All Steel) tires. These tires are made with steel sidewalls. Many thousands of miles later I traded the trailer for my present Airstream without any more blowouts on my Alpha.
I have another question that does not appear to have a good answer....If trailer tires are so good and must be installed on a trailer when truck tires wear so much better, what is the rational for requiring the ST's on a trailer? My truck, 2002 GMC Duallie uses LT tires and I can not wear them out not blow them out before I feel it is safe to replace them (7 years). I am running LR-E' LT types on my truck.
I am sorry to say that I do not agree with the idea that ST tires for trailers is the safest and best option.
I have never seen any "requirement" that trailers run ST type tires. However, ST type tires can only be installed on trailers, so that might be the "requirement" you are thinking of.
The selection of tires to use on any vehicle is up to the RV company. As far as I can see they select tires based only on load capacity, physical size and cost. I don't know what the RV company actually pays for ST tires but it is probably less than an LT of equivalent load capacity.
If your only concern was for lower cost when comparing two tires of equal load capacity and the ST tire was easier to fit (it was smaller and did not require you make larger wheel wells), Why would you select the higher cost tire? If you don't offer a meaningful warranty, you do not face the expense of warranty costs if there is a tire failure so what is the incentive for the RV company to spend more?