Rearend/wheel question

[eversmann79]

If I were to custom order a 9" that's one inch wider on each side would that mean I could run 1" deeper back spacing wheels?
I want boss 338 wheels but have heard some troubles about fitment

 

[eversmann79]

anyone know>?

 

[khan0165]

generally, anything past 4 inches of backspacing on a Gbody is pushing your luck. There are many cases where 4.5 or even up to 5 inches has worked without any modifications.
If you've had a frame repair, you may even have less than 4 inches available.

So really, you can't be sure unless you get under your car and measure everything out.

But by theory, you should be good for 5 inch backspacing with a 2 inch wider rearend.

 

[78MC-BBC]

a lot of the backspacing questions also differ by what model g-body you have? i know on my 78 i am running a 5" backspacing on a set of 17x9.5 centerline wheels and have no problems with the wheels hitting the frame or body and i am running a stock 8.5" rear axle

 

[jrm81bu]

It seem as the diameter goes up, you can get away with more backspace(which really doesn't make sense). My 16x8 with 4.75 bs needed a spacer. My 17x8's with 4.5 had plenty of room. And my 18x9.5 has 5.5bs, which i'm currently running with 1" adapters, however 1/2" spacers would work(which would give me 5" bs).

 

[khan0165]

alot depends on tire sidewall buldge as well...
on smaller rims, a taller tire is used and usually has more sidewall buldge. As rims get larger, the tires become more low profile, and the sidewalls buldge less.

for example... two rims, 15" and 17", both 8" wide, both 9" tire tread width. The sidewalls may stick out to 10" on the 15" rim, where only 9" on the 17" rim.

 

[eversmann79]

I have a 78 regal.
I really just don't wanna buy these rims and mount 275 tires and have them go to waste because they don't fit.
Rims are 5" BS and 275 tires

 

[mebe007]

I have a 78 regal.
I really just don't wanna buy these rims and mount 275 tires and have them go to waste because they don't fit.
Rims are 5" BS and 275 tires

no way in the world your going to fit a 275 under the back with 5" backspace. i have an 80 and its the same wheel well. its tight in there with 4" of backspace. you could run spacers and thats about it.

now if the axle is 1" wider on each side then yes those 5" back space wheels will fit like a 4" wheel on a stock width rear.

 

[jrm81bu]

I have a 78 regal.
I really just don't wanna buy these rims and mount 275 tires and have them go to waste because they don't fit.
Rims are 5" BS and 275 tires

no way in the world your going to fit a 275 under the back with 5" backspace. i have an 80 and its the same wheel well. its tight in there with 4" of backspace. you could run spacers and thats about it.

now if the axle is 1" wider on each side then yes those 5" back space wheels will fit like a 4" wheel on a stock width rear.

You wouldn't think that it would, but 5" bs on mine would be perfect and it's even lowered. It has 255/45/18's now and I have 275/40/18's that will go on when the others are done. There may be a need for some small spacers, but other people have already done it.
Like I said earlier, rim diameter makes a big difference. I agree that a 275 on a 15" rim with 5" bs will not fit, but an 18" rim is a different story.

 

[eversmann79]

so 275/40/18 will work jr?