Originally Posted by markbvt
People air down offroad-oriented tires (which typically have stiffer sidewalls), and if it's a big bike, they usually only go down to 22psi or so.
Stiffer sidewalls is certainly an aspect of offroad tires. I don't think you can count on them to protect your rims from under inflation though. Bikes (big ones even more so) require "appropriate" inflation for the circumstances. This is a moving target based on your suspension, tires, road conditions, gross vehicle weight, and all the other things I'm not thinking of right now.
I've never bottomed out my suspension, but I'm a little guy who likes to keep both tires connected to the ground and I try to ride in such a way that the front end is light when I hit obstacles and heavy when I'm in turns. If there is an obstacle in a turn, I slow down. Not terribly complicated.
I suggest Mitas E09 tires. The carcass of the tire is STIFF. My hands are still sore.