Backspace to fit 12" rim on mini tub foxbody

[NightMare Fox]

Just as the title says...im looking to find out the correct Backspace to fit a 12" rim under my car. the car has mini tub done and coilovers.....im hearing anywhere from 6" to 7.5" BS when i have done some searches on other forums...thanks guys

 

[Speedy]

Depends on if and how much the rearend has been shortened

 

[Fryguy302]

Typically, if it's a fox rear end in a fox car and it's been shortened until the 9" end is all the way against the lower control arm mount, the car will use a 15x12 with a 6.5" backspace. Some will also use a small spacer, depending on the tire being run.

 

[NightMare Fox]

Depends on if and how much the rearend has been shortened

well it has not been shorten...is that a must?

Typically, if it's a fox rear end in a fox car and it's been shortened until the 9" end is all the way against the lower control arm mount, the car will use a 15x12 with a 6.5" backspace. Some will also use a small spacer, depending on the tire being run.

it has a 8.8 and not shortened

 

[Fryguy302]

well it has not been shorten...is that a must?

it has a 8.8 and not shortened

Kinda weird to not shorten the rear end, that's really the purpose of the mini tub, and also what makes the mini tub look cool.

If it's not shortened at all, a 12" wheel would be like an 8.5-9" backspace, which probably doesn't exist. Best to shorten the rear end.

 

[NightMare Fox]

Kinda weird to not shorten the rear end, that's really the purpose of the mini tub, and also what makes the mini tub look cool.

If it's not shortened at all, a 12" wheel would be like an 8.5-9" backspace, which probably doesn't exist. Best to shorten the rear end.

i was told by someone that it could be done without shortened but will do it if needed.......if so where is good place to have it done?

 

[Billydroveit]

i was told by someone that it could be done without shortened but will do it if needed.......if so where is good place to have it done?

I've seen it done with a 7.5" backspace wheel on a 10" rim, but not a 12. Take 2.5" off the axle and use a 6.5 BS 12" wheel like Raj said. If you're going to stretch a 28x10.5 tire on there you can get away with only 2" off the rear. To run a W tire or more you need the extra 1/2" off the axle.

 

[TWISTED]

I tried a 7.5 backspacing on a 12" rim but it stuck out too much. Keep in mind the crazy backspaced rims have a weird barrel shape that won't allow some brakes. My wilwood's would fit. Not even close.

 

[NightMare Fox]

Typically, if it's a fox rear end in a fox car and it's been shortened until the 9" end is all the way against the lower control arm mount, the car will use a 15x12 with a 6.5" backspace. Some will also use a small spacer, depending on the tire being run.

I've seen it done with a 7.5" backspace wheel on a 10" rim, but not a 12. Take 2.5" off the axle and use a 6.5 BS 12" wheel like Raj said. If you're going to stretch a 28x10.5 tire on there you can get away with only 2" off the rear. To run a W tire or more you need the extra 1/2" off the axle.

ok so you guys are saying 2.5" total 1.25" per side shortened......with a 6.5 BS....here is my next question what spline 33? im doing a stroked LS lq4 6.0 and adding a 88mm turbo looking around the range of 1000HP thanks for any info

 

[Fryguy302]

ok so you guys are saying 2.5" total 1.25" per side shortened......with a 6.5 BS....here is my next question what spline 33? im doing a stroked LS lq4 6.0 and adding a 88mm turbo looking around the range of 1000HP thanks for any info

33 will be fine for that power range, but at 1500, you will probably destroy the 33s and need to go to 35s. Also for the 12" with 6.5" bs, bring the 9" end all the way to the lower control arm mount. That distance may vary depending on the rear end, but it is likely around 2-2.5".

 

[NightMare Fox]

33 will be fine for that power range, but at 1500, you will probably destroy the 33s and need to go to 35s. Also for the 12" with 6.5" bs, bring the 9" end all the way to the lower control arm mount. That distance may vary depending on the rear end, but it is likely around 2-2.5".

Ok maybe I should just go with the 35 than as I'm sure she will be turn up at some pointe building the motor to handle 1400-1500 never know where I might end up ..better safe than sorry

 

[Fryguy302]

Ok maybe I should just go with the 35 than as I'm sure she will be turn up at some pointe building the motor to handle 1400-1500 never know where I might end up ..better safe than sorry

Makes sense. On mine, I went through 31s, 33s, and now 35s.

 

[NightMare Fox]

Makes sense. On mine, I went through 31s, 33s, and now 35s.

nice not looking to keep replaceing lol....thanks again Raj

 

[Billydroveit]

ok so you guys are saying 2.5" total 1.25" per side shortened......with a 6.5 BS....here is my next question what spline 33? im doing a stroked LS lq4 6.0 and adding a 88mm turbo looking around the range of 1000HP thanks for any info

2.5 each side Liek Raj said it bring the end flange to the lower mounting point.

 

[NightMare Fox]

2.5 each side Liek Raj said it bring the end flange to the lower mounting point.

I do not see where Raj said to do 2.5" i am seeing 2-2.5" is about what is needed....Billy is your car mini tubbed? if so is that what you did 2.5" ????

 

[Billydroveit]

. That distance may vary depending on the rear end, but it is likely around 2-2.5".

My car is not mini tub, but i did my homework when i was looking at that route.

 

[Billydroveit]

SO if you measure where the flange is now, to the lower controll arm mounting point it ends up being 2.5 is usually the max you can take off and still be able to use the standard mounting point. Now take what a factory set up is with a 10" wheel and it needs a 6.5 backspace. So to add 2 more inches of rim will require a minimum 2" less axle length. Now factor in afermarket brakes are usually thicker than teh drum set up so you want to also compensate for that in the process and buy yourself as mush sidewall room you can since usually you lower the ride height at the same time which means you have to clear the bubble of the side wall at a wider point, thus using up that extra 1/2" over the 2" required just to clear the added rim width.

 

[NightMare Fox]

SO if you measure where the flange is now, to the lower controll arm mounting point it ends up being 2.5 is usually the max you can take off and still be able to use the standard mounting point. Now take what a factory set up is with a 10" wheel and it needs a 6.5 backspace. So to add 2 more inches of rim will require a minimum 2" less axle length. Now factor in afermarket brakes are usually thicker than teh drum set up so you want to also compensate for that in the process and buy yourself as mush sidewall room you can since usually you lower the ride height at the same time which means you have to clear the bubble of the side wall at a wider point, thus using up that extra 1/2" over the 2" required just to clear the added rim width.

ok great info there i apreciated it....thanks Billy