Here is some very good info from an RV site. I did some research last year after a couple of blow-outs. 16 inch are way better than 15 inch. Get the highest ply that you can afford. If the tires call for 70 pounds run them 8-10 pounds higher. As said above HEAT is the biggest killer. Don't even listen to what the open trailer guys recommend. The weight on the inclosed trailer is WAY heavier than them and then we add quads, generators, tools, cupboards, and any other thing we can think of. I ran my old open trailers on junky mobile home 14.5 tires for years and never had a problem. I have 15 inch on my trailer so I went with the best Carlyle they had and in 4 years I will buy new tires and put these on Craigslist. http://www.rv.net/forum/index.cfm/fuseac...%7B%7D/sr/1.cfm