say the correct 15x8 wheel for my car needed a 5.5" of backspacing, if i wanted to use a 15x7 instead would i take one inch off the BS cause the wheel is 1" narrower? if so would 15x7 with 4.5" BS be correct?

 

i know there are smart people on here, someone help me out so i can order my wheels.

 

my sport coupe has 15x7 draglites in front and 15x8 in back both with 4.5" b.s...fits perfectly. For the strip, I have another set of 15x8's with 275/50/15 nitto drag radials mounted on them and that looks mean as hell and its the same 4.5" b.s on those too...and if you're wondering if the drag radial sticks out...NO. I could probably put a 295 radial under there with the same b.s and it would be just flush with the fender lip.

 

Cosmetically, it doesn't matter what it looks like on the insides of the fender. The wheel should stick out so the outside of the tire is always in it's normal position. This means changing the backspace to best achieve this look. Technically, moving it out so that the tread is just under the fender lip will still look normal unless a very narrow tire is used.

My 15x10's have 5.5 backspace but then the tires are so wide that they stick out anyway. My backspace is mainly to keep the tire from rubbing on the inside fender. I'd love to tuck them in some more but have no more room.

The outside of my rear tire doesn't track in the same track as the outside of the front tires

 

well i didnt mention this before because its "not thirdgen related" but since i know a lot of people on these boards know these kinds of things i posted it here. i was asking because i am putting draglites on my 87 T bird and want to run a 15x7 wheel, the correct back spacing on this car for a 15x8 is 5.5", but i wasnt sure how to figure out what back spacing id need to get a 15x7 to fit the same.

 

An 8” wheel is usually 9” wide lip to lip, meaning that 4.5” backspacing is 0 offset, 5.5” is 1” offset.

If you’re looking for the same offset on a 7” wheel, 8” actually, 4” BS is 0 offset, and 5” is 1” offset. That offset/backspacing will put the tire in the same location in the wheel well as the 8" is putting it.

If you’re looking to put the outside edge of the rim in the same place as the 8” then the 8” rim had 3.5” spacing in front of the flange, so with the 7” rim you’ll need a ½” offset or 4.5” backspacing.