As high as 65 rear with camper stuffed full of gear (highway) or hauling firewood, 35 empty highway, 25 with camper off road, 15 empty off road.
Little update: 65psi was too high, and wearing the tire centers. I'm now down to 42psi rear 40psi front with even wear, and no undue tire heat. Speaking of wear, I'm getting ~2400 miles per 1/32 of tread, not great but could be worse. The truck weighs roughly 6500lbs on a trip, nearly balanced front to rear, with no funny tire wear issues. Off road, 20psi works well all around with the camper on board and driving slow. I'll add, these Falkens are really a great tire until you encounter mud. Then it doesn't matter if aired down, they do not grab. My rear axle is locked and it still just churns with no bite. Rocks? They're great, wet or dry. But the low void tread loads up quick in mud. For reference, my last set of tires were BFG AT KO, in a 33x10.5, and those blew these Falken AT tires away in mud. I prefer the Falken everywhere else though.