Wheel backspace fitment need help

[FOOT]

Wheel and tire guru's I need some help. Looking to get 15x10 Rims(P275/50R15) & 15x12 Rims (P325/50R15) for the rear. I have no clue how the size works for clearance. My Volk TE37's were 18x10.5" -22 offset and they fit perfectly. The rims I want come in backspace measurements...

Heres a backspace vs offset chart
http://www.jeepkj.com/forumpics/wheels/offset.gif

[frankiman]

you can't fit 15" rims on a GTR
it won't clear the brake caliper

other than that, the rotor hat is so large, back space should not but an issue

[FOOT]

I'm not going to be using GTR brakes on the front. Aerospace has a street/drag brake setup that will clear 15" skinny's. I know the 2 piston rears will clear 15"