Since weight is not an issue Id go Radial. Reasons1. Trailer “ST” tires maximum rated speed 65mph. Might be a few exceptions, but Ive never seen one. I drive 70+ for hours to and from the lake.2. “ST” tires are not made with braking as a concern. I suspect you have brakes on your trailer and you expect them to help stop the trailer to the best of the tires ability.3 “LT” tires are a great option but probably more expensive. Id find a good inexpensive radial tire. If you put a lot of miles on the trailer (6,000 per year or more) then worry about mileage warranty. Otherwise you will probably replace before you ever get to 30,000 before they start needing replacement due to age. Just my thoughts..