how important is that .XX backspacing?

Got a set of free 255/70/16's from work and im ordering new rims. 16x8's, but im not sure on the B.S. From what ive read everyone recommends 4.5. With a 2in BB will this rub? (its my DD, no trail useage), but i want a nice ride. I am planning on getting 31's soon though, so this does matter.

I come up with a a 30X10-16. I ran the stock 5.25 backspacing on 31X10.50-15, 32X11.50-15, and 33X12.50-15's. I didn't have problems with any of them except for the tires rubbing the control arms on all three. The 33's were the worst.

If your going up to 31's (? width) I would probably stick with something around 4.5. The tires your looking at I think would be fine on the stock back spacing but they might rub slightly at full lock.

anything bigger than 10.50 with stock bs you run a good risk of rubbing your leaf springs. dont know how lincoln ran 12.50s, but most people cant.

I run 11.50's with 4.0 back spacing and I think my tires stick out from the fenders to far. they have never rubed though.

good deal, i know what i need now. I suck at math, so unless i sit down and TRY, i cant do the metric to sandard conversions very well.