Back when I had Rubicon wheels and tires on my xj, I once aired them down to 11# in the snow. On a steep descending obstacle, the bead found it's self shifted off of the wheel, but just not enough to lose the air out of it.
Detour is the one that noticed 1/3 of the bead was just hanging on to where it was about to pop off of the rim. The line that was taken would have put just about any tire bead to the test.
Getting back to the original question, I ran mine at 32# on the street if I remember correctly.