Re: proper psi for 285 70 17 E rated BFG's
IIRC for removing and refitting, could be wrong though.
As for proper tire PSI, that depends on a lot of things (extra vehicle weight, weather, etc). I run load range E 255/85r17s and run 41 PSI up front and 42 PSI at the rear. This has shown to be the best for my truck and tire, as it is set up currently, via chalk testing. The best thing you can do is start around 40 PSI, which is about the average of what I've seen on E range tires, and tweak it from there with a chalk test*.
*Google "Chalk test tires". I would provide a link, but my phone is being moody.
'12 Toyota FJ Cruiser, Cavalry Blue, Toytec BOSS Suspension w/h 5160 Rear Shocks, 255/80r17 KM2s, Defensive Designs Sliders "The Warturtle" *DD/Backup wheeler*
'88 Ramcharger, Blue and Silver, 318, 727, NP241, 4" lift, 33x12.50x15 Goodyear MT/R Kevlars "Hannibal" *Trail pig*
Virginia Krawlers, TeamDOHC Offroaders, RCPFA, NCFJC,