backspacing??

ive been talking to some people about puting a lift on and fitting 33s under it people say i would clear it easy and not rub with fender trimming and backspacing? the problem is i have no clue what backspacing is if someone could help me out that would be great. also the prices of doing it to the cost?

If you're wanting to run 33's with no rubbing at full articulation then you're going to be looking in the range of 6 inch lift without any cutting or backspacing worries. If full 6 inch is to much or to costly you could pull it off with around a 4.5 inch lift with fender trimming and backspaced wheels to prevent rubbing at full turn. Backspacing refers to the wheel's offset opposed to the center of the rim. Easiest way to visualize it is to think of a bare rim laying on the ground face up and measuring from the ground to the center mounting point. The higher the backspacing the farther the wheel sticks out to help combat rubbing when the steering is turned full tilt either direction. Give it time and either aloha or saudade will chime in with more info. I'm running 3 inch lift and 31's with no trimming or backspacing and I don't rub at all. In my pic that's the front end at current full articulation and still didn't touch anything. When doing a lift don't forget to take into account the drivetrain's change in angles, you will definately need to get a SYE (slip yoke eliminator) and CV (constant velocity) drive shaft. I've read alot online that people say the front cv driveshaft can be used in the rear with a sye but haven't personally tried it. One of these days I'll be giving a few of the hints you can find online a try to see how well they actually work.

Backspacing is the distance from the inside edge of the rim to the hub mounting surface. Stock XJ wheels have 5.25" BS. That means that the measurement from the hub mounting surface to the inside edge of the wheel is 5.25". Most aftermarket wheels are in the range of 4.5" to 3.75" of BS. That means that they will stick out further in the wheel well than stock wheels.
As Dave said, to run 33s you are looking at a minimum of 4.5" of lift and thats with sheetmetal trimming and longer bumpstops. If you plan to run 33X12.50 size tires you'll also need to go with an aftermarket wheel thats at least 8" wide with around 4"-4.5" of BS or a set of spacers to push your stock wheels out further.
Its not a cheap proposition to lift enough for 33s on an XJ, if you do it right. You're looking at a long arm kit or drop brackets, SYE and CV driveshaft, as mentioned, probably new wheels and probably a regear.
Time to wear out the credit card.

Oh yeah, The front DS can be used in the rear with a SYE, Ive got one on my XJ. Its a good fit with around 3-4" of lift, above that, the ds is a tad short.