I normally run 3 to 4 PSI, unless I am going to be driving it back and forth to work and will be only seeing pavement for a while then I wll pump them up to around 13-15 PSI.
When I ran Sand Lake, I ran 5 PSI at first then lowered back down to around 2-3 PSI. I have 32X10.50 swampers on 15x7 wheels.