Also curious what he should air down to. Beadlocks and 37's are on my list..
I've been airing down to 10 psi with 35 X 15 GY MTR's. So figure you could go lower than that.
Depends on the tire. For something like a BFG or GY MTR, I wouldn't go lower than 10 psi as their sidewalls are thinner and don't need to go lower. On something like a Toyo MT or Nitto Mud Grappler which have super thick sidewalls, 6-8 psi is pretty standard and you'll still have people telling you that you're not aired down enough.
When I ran 40" Goodyear MTR/K's (C load rating), I did run down to about 8 psi if my jeep was not loaded, an example would be when we did the Florence Junction Run; I had no doors, no passenger, very minimal tools and recovery equipment, so about as light as my four door could be. As Wayolife states, the MTR/K's have very thin sidewalls so you don't need to air down as much. During an event like a JK Experience when my jeep is at its heaviest load, 10-12 psi was plenty low with the Goodyears and their C load rating.
Now that I am on 40" Mud Grapplers (D load rating) i run very low psi, last weekends "Back way to Crown King" run, I was down at 6 psi because I had no weight in the jeep and probably could have dropped another pound (maybe two). At my heaviest weight during the 2012 JK Experience, I safely, and comfortably, ran 8 psi for the entire event.
As for Arizona having sharp rocks, yes we do, Wayolife and Bleadbeet have experienced this first hand. I went through two MTR/K's in a weekend (tires had maybe 10k miles), while the guys running Toyos and Nittos had zero issues. One of the reason I went back to Nittos.
