stock YJ wheels are 15x7, and the backspacing is somewhere around 5"
if you look at tire manufacturer specs, most if not all will say a 7" wheel is too narrow for a 33x12.5 - though in real life, some people run them with no noticeable issues at all.
most mfrs will call for a wheel 8-10" in width for that tire.
on to the other issue of backspacing and rubbing on a wide tire. I'm currently running stock wheels with 31x10.5 tires and I rub slightly at full lock. For me, it's far enough at the end of the turn that I don't bother with adjusting the steering stops - if I hear/feel it rub, I just back off the wheel a little. if I were running a 12.5 on the same wheels I'd definitely have to do something about the backspacing because I feel adjusting the stops for that combination would lose too much turning radius.
you CAN run spacers and in reality, if you get a decent spacer and they are torqued properly upon install (and loctite is used on the studs holding the spacers on) you'll be just fine. the nay-sayers will often comment how a spacer adds leverage to the wheel and will shorten the life of your bearings... true to a point, but no more leverage than using a wheel with less backspacing.
but for about the same cost as a set of decent spacers, you can get a set of brand new set of steel wheels in 15x8 with about 3.5 - 3.75" backspace and be ahead of the game as you'll now have a proper size wheel for the tires you've got mounted
[FONT="Comic Sans MS"][COLOR="Blue"]Sean B. - Schenectady, NY - 95 YJ, 350/700r4/NP241, JB Shorty SYE, 8.8 rear, 2" BDS, 1" homebrew shackles, Daystar 1" BL, TJ flares, 35x12.50 General Grabber AT2 on 15x10 Bart D-Truckers, Polyshield polycarbonate windshield, HD over/under crossover steering
[/COLOR] [COLOR="Red"]swap/build thread: [url]http://www.jeepforum.com/forum/f22/after-almost-4-years-finally-my-own-build-swap-thread-1542284/[/url][/COLOR][/FONT]