I'm trying to find out what I need to do to fit a 12.5" tire on the backside of my 87' Formula. Any suggestions on backspacing and mods would be helpful.

 

To start with....Do you have a 3rd gen or 4th gen rear end?

2ndly, do you have/want 3rd or 4th gen backspacing wheels?

3rdly, you can cut off the rear bumpstop from the body, beat the inner panel in in the middle & cut a little from the front & rear.

12.5" under the fenders & without totally cutting out the inner fenderwell & modding the interior is almost a tall order. Would have to figure everything PERFECT to not have to touch the interior.

EDIT: You said tire, not wheel. In that case, not nearly as hard to do, just still have to figure it right, but I dunno tires near as well as wheels.

 

I have a 3rd gen rear end and looking for 3rd gen backspacing. I probably won't go with any larger than an 11" wheel and I'm looking to fit a 305-315 tire. I'm tossed up between Rally II's or Snowflakes from Year One in 17" or 18"