JJ,
Many fifth wheel trailers and heavier travel trailers come with ST tires from the factory. Good year states on their websites their own LT tires are suitable for direct replacement as long as the wheel rating is not exceeded.
Kumho builds a commercial LT tire they recommend as a "highway rib all position tire" that is "also recommended for trailer use". This is the 857, which is available in sizes that make it appropriate for smaller trailers.
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you stated:
"Why are almost every LT tire that is classified for a RV’s are speed restricted to 75 MPH even though the sidewall is marked differently???"
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You will have to clarify that statement for me, because I don't understand what you mean ? What I do know is there is a huge selection of LT tires available in 15 and 16" sizes that are speed rated Q or R. That is just under and just over 100 mph. It is still up to the buyer to do his homework and choose all the different performance aspects he needs in a given product. So if a 75 mph speed rated tire is not adequate for the job, then that product would be deleted from consideration. I guess it goes without saying, if a 75 mph rating is not adequate, then a 65 mph certainly would not be. Here is a little side note, on speed rated tires, I took the ST tires off my camper that came OE, and they were actually speed rated ( according to the tire company ) 100 kph, which is only 62 mph.
Glad to see this discussion continuing. There are several folks here that are sharing some really good info on a very important topic regarding safe towing. After all, I believe that is ultimate goal we are all trying to share with one another: what is the safest way for us to get our trailer down the road, with the least likelihood of having to be dangerously stopped at the side of the road doing a unnecessary repair"