Sorry I got here late,
My sidewalls say 55 cold, I run 50 on road. good way to check is lay some flour down and drive over it, if more is on the center of the tread, let some air out, if more is towards the outer fill em up a bit.
If I'm running aired down for comfort and not technical requirements I run 25.
If its rock crawlin I'm around 13 to 15. Wouldnt reccomend that low if you are running alloys though, my steel just bends and I sledge hammer it back till it holds air, alloys will crack and gouge. I wouldn't go under 20 with alloys bro