My Flagstaff 25' is killing me on tires, but here are some lessons learned: Tires only a few years old should be replaced if there is a possibility that they have deteriorated. My tires, 13", were original, 3 years old, with little wear, and little cracking when I bought the camper. On my second trip, in a small town at 6 PM on Friday 300 miles from the house, one tire came apart and a second was lumpy enough to let me know it was next. I managed to get home on 2 ill fitting replacements. My speed was conservative, about 60 mph or so behind a GMC Sierra 5. 3l.
Since replacing all tires, I had a new one come apart, all the way apart, at 70 mph on a hot day behind the Dodge. It had only 2000 miles on it. It may be that 4 tires at the 1360# load rating for the ST175/80 R13 is too close to my tow weight, 4000# empty/4500# loaded.
Lesson #1: I would put 14" or 15" tires on my camper if they would fit. A larger tire would run cooler.
Lesson #2: This one could be stupid, but I'm suspicious that excessive trailer braking could be weaking the side walls/belts/plys on the new tires. I had the feeling that the camper was actually braking the truck and trailer. That can't be good. I plan to limit trailer braking.
Get new tires and good luck!