If i run a 15x12 wheel and the rear is narrowed 2.5" per side what back spacing will it need to be? Is it the same as with a 15x10 or would it be different?

 

Mini Tubs?

 

My understanding is if your running a 15x10 with 5.5 BS and you want to run a 15x12 wheel you would need to have one with 7.5 inch BS. Someone please correct me if im wrong

 

Without a narrowed rear the 15x10 needs a 7.5" backspace. A 15x12 would need 9.5 backspacing (which they probably don't make)

So what you will need to do is find out the max offset you can get on the 15X12 and then subtract that from 9.5 and thats how much you need to narrow the rear on each side. Also order some minitunds and relocation brackets for everything.

 

cwaldt, a STOCK wheel has 7.5" back spacing for stock width rearend, so with it narrowed 2.5" per side that would move the backspacing back 2.5" per side also. thats on a 10" wheel though, not sure on a 12" wheel.

already have the rear suspension correct and its getting tub'd and everything, just wasn't sure on the offset on the new wheels.

 

5.5" or 6" b.s. From measuring mine, I would say 6" b.s. will be close to the trailing arms. Mini-tubs, right? Stock lower trailing arms? I have BMR tubular lower trailing arms, with the spacers re-cut to move the them inboard for more tire clearance. After the tubs are installed, those are the next thing in the way of the tires. Looks like I gained close to an inch over stock lower arms.

Good luck, Ed

 

I'm running Wolfe LCAs with the offsets, moves the LCA 1.25" inboard. it is getting mini-tub'd also.

 

The back spacing will depend on how close the tire is to the lower control arm. If your rear is narrowed and you have a 10" rim with a 5.5" bs. And the tire is real close to the control arm. Then your 12" rim has to have the same bs. If you have over an inch gap then your 12" rim can have a 6.5" bs.

 

I didn't realize you had already narrowed the rear. I thought you were just trying to figure out what b.s. you needed. I went with some 15x10 w/ 4.5 b.s. & a rear end narrowed 3" per side.

 

I think 6" should be fine for you. Mine is narrowed 3" on each side, and it looks like 6" is going to be close. I have 10" wheels on it right now because I had been running 9" X 30" tires. The 30" X 10.5" tires have more of a bulge in the side walls on the 10" wheels I have now. I'm going to 12" wheels, which will pull the side wall bulge in some compared to the 10" wheels. I'm thinking 12" X 6" b.s. will clear mine just fine. You should have 1/2" more than I, so I would expect 6" back spacing to be fine for your car. I like the tires in as far as I can get them.

Good luck, Ed