When towing, I pump mine up to 80psi when they're cold (before rolling for the day), that's the max psi and they will carry their max payload with that... and while I am not loaded to max payload of the tires, I still air 'em up to 80psi. Carrying less payload isn't going to hurt them; yea the ride may be stiffer, but I'm towing heavy anyway so it's not that stiff, and the tires feel more stable since there is less flex on them. As far as more wear on the center of the tire, I haven't experienced that.