I have a tracker trailer (17.5' alum boat / 50 HP motor) 1st. set of tires (Tracker tires came with trailer MFG. in china) ran 40 PSI got less than 1,000 road miles on them, BassPro out of the goodness of their heart replaced them ( AT NO CHARGE) with the same type tire informed me tire psi should have been 50 psi got less than 800 miles on the 2nd. set of tires. Like you said the inside was gone while the the out side looked new. On my 3rd. set now that I bought from Brothers Tire store in Kannapolis have app.1400 miles on them at 45 psi and they still look new. ( I'm sure they were mfg. chain.) so I'm going with the 45psi. Most of the roads I travel to High Rock are a lot like a washboard, real rough.