The most important number on a trailer placard is the gawr for tire replacement. Weigh your trailer and make sure that you are not over this number. Side to side weights are an extra bonus. Then go to a good commercial tire shop and purchase the best tire you can find or efford that meets the axle requirement. Avoid ST tires if at all possible it you plan on seeing America and want to put tire problems behind you!
Like Jimnlin says the trailer manufacturer may have provided low bidder tires OEM and has no vested interest in suggesting anything different. The commercial tire shop on the other hand has a lot invested in insuring that what he sells you will perform over the years for you.
All the government document in the country will not meant as much as that knowledgeable tire dealer. Or as CapriRacer said one can just listen to those on forums like this that have had great sucess with what works in the real World out on the highway.
Chris
