I have 13's under my 20' MA on a dual axle trailer. I have towed it ~100 miles on one axle in November in New England. (Broken spring when I bought it) Tire temp wasn't an issue, but load was probably 1000 lb over what was rated. When it is 95F up here and I tow ~130 miles, the tires get warm, but no problems. (Now I use all four!)Of course the asphalt is like 130F or more in July.
Everything else equal, radials should run cooler. I *think* I have Kenda LoadStar K550 tires- they are radials. Looking online, they are 1360lb rated.
http://www.kendatire.com/en/specialt...loadstar-k550/