Optimal backspacing for a 15" wheel (ONLY) with disc brakes? drag tire size is 28"x9"x15"

[BUICKTIME]

Like the title states, only looking for recommendation on backspacing for a 15" rear wheel with a car that is running rear disc brakes on a drag tire. Rim width either a 15x8 or 15x9 in a non-modified wheel well (I may have to roll the inner fenders). The tire is a Mickey Thompson Pro Bracket Radial 28"x9"x15" with a full width 9" rear end with Strange disc brakes (but should be no different than an 8.5). The car will sit low with the tire sitting in the wheel well. Please post pics of how the car sits and the details of your setup. I know I am being a little specific as I only want to know about 15" rear wheels ONLY....

thanks in advanced guys

 

[dynoman]

in a non-modified wheel well

Depending on how low the body sits , you may need to bump in the upper portion of the wheel tub . You can check it by removing the rear springs and jacking the rearend through full travel . I found that where it looked like it would clear , would rub when turning and hitting a slight bump at the same time . I'm a big fan of tucking the rear tire and the 8" or 9" rim will help with that . A 10" rim makes the sidewall bulge more .

 

[BUICKTIME]

A 10" rim makes the sidewall bulge more .

What offset do you have & any mods to your wheel well? & do you have disc brakes?

 

[dynoman]

My 9" is narrowed 1.5" each side with drum brakes . my wheels are 15x10 with if I remember correctly 4.5" backspace . I did a frame notch that brought the frame face flush with the wheel tub . I had to massage the upper wheel tub with a sledge hammer to gain the needed clearance because the upper tub tapers in slightly . The fender lip is rolled also .

 

[dynoman]

I had this tire on and also a
295/65-15 . They were tight .

 

[BUICKTIME]

My 9" is narrowed 1.5" each side with drum brakes . my wheels are 15x10 with if I remember correctly 4.5" backspace . I did a frame notch that brought the frame face flush with the wheel tub . I had to massage the upper wheel tub with a sledge hammer to gain the needed clearance because the upper tub tapers in slightly . The fender lip is rolled also .

Looks like they did a nice job, and the tire is sitting in there just right. That's a nice size tire too.
The reason i'm asking is because I ordered a set of rims with a 4" bs and was second guessing myself if I should have gone with a 4.5" bs and maybe a small spacer if needed. I may just have to roll the lip and call it a day.
Thanks for the input Dynoman...

 

[dynoman]

The frame notch was easy , that's my son cutting out the frame . We used 1/4" plate for the notch . We used the cut out piece of frame as a template & traced it onto the 1/4 plate then cut it out with a plasma cutter . A little grinding to fit and welded it in .

 

[THensley]

I run 28X9 PRO BRACKET 4 in backspace no finder mods OE replacement MOOG spring (not cargo spring) never rubbed 18 lb air
I think ill have to roll finder to run ET street PRO

 

[THensley]

8" wheel 4" BS will fit most every even thing even MT ET street R , but the 275 ET street Pro or Hoosier DR probably need finder rolled
10" wheel and 4.5 will be new every thing under the back

 

[BUICKTIME]

8" wheel 4" BS will fit most every even thing even MT ET street R , but the 275 ET street Pro or Hoosier DR probably need finder rolled
10" wheel and 4.5 will be new every thing under the back

Exactly what I was looking for, thanks. I'm running the same size rim and tire as you. I have a few fiends running strong on Pro Brackets and they love'em.
I plan on setting up the car pretty low, nowhere near as low as a low rider but drag style low without sacrificing dead stop launches. So, it looks like the inner fender lips will have to be rolled either way.