What back spacing for a 75 cutlass 17" s/sII wheels year one

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What back spacing for a 75 cutlass  17" s/sII wheels year one Empty What back spacing for a 75 cutlass 17" s/sII wheels year one

Post by stich626 on Wed Oct 30, 2019 7:46 am

Hello, first post.
I am looking at the Year one 17" olds super stock II cast alum wheels for my 75 Cutlass.
I buy one gift for myself over the holidays as my birthday is days after Them.
Year one list 2 different sizes and back spacing, 3 different sets without getting into the g body only listing
They are
A)8"wide 4.5" backspacing set of 4
B) 9" wide 5" back spacing set of 4
C) (2) 8" w 4.5"b/s and (2) 9"w 5" b/p set .

Car is not lowered, and have no plans on it, only lowering is the 45 year old springs setting(sagging) .

What fits, ? do both?
It seems (I could be wrong) that the stock tire size was hr70-15 that from what I can find is a 235-70-15
If so that is a 28" tall tire.
If this is correct. Even with a 17" wheel will still have 5" of side wall. and not look like tiny rubber bands.

Am I on the right path?
I'd rather the wider wheels and same oem tall tire if possible . And stay away from staggered width wheels.
So. what wheels will fit and what tires?
Thanks for any help.

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What back spacing for a 75 cutlass  17" s/sII wheels year one Empty Re: What back spacing for a 75 cutlass 17" s/sII wheels year one

Post by impalamonte on Wed Oct 30, 2019 8:40 am

I have a Monte. But , same basic architecture.

Rims : 5.25" of backspacing

Front 18x9.5 rims on 255/ 50. no rub.  
Rear , same size rim , 295/45 with 3/8" clearance between sidewall and fender lip , spring slightly compressed. no rub.

https://www.g3gm.com/t8709p75-update-1973-monte-carlo-body-off-frame-resto
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Post by thatfnthing on Wed Oct 30, 2019 9:39 am

The problem is the dimensions of tires are nominal, sometimes wildly so.  A 255/50 of one tire will be a different actual width and height than a 255/50 of another make/model of tire, even from the same manufacturer.  Further, while our cars are 'close', there will be some variances in wheel well size (the Chevelles can apparently swallow a 315 tire, while I know I can't stuff that big a tire in the Monte without rubbing on something), and your suspension travel may be different than the next guy's.

So you can't rely on just the math, there will be some trial and error.

That said, I run 17x9's (6" backspacing) all the way around with 275/40 in the front and 275/50 in the rear, so the 8's and 9's you mention should fit fine width-wise.  However, it would be best if you had a wheel to test with, either one of those or a different style with the same dimensions, just to be safe.

Then you can try the math to find a tire that fits the wheel, but guaranteed it will vary, so if you can get the actual tire dimensions from the dealer, it will help you make a better determination.
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Post by impalamonte on Thu Oct 31, 2019 11:45 am

Agreed thatfnthhing....my fit on the rear was definitely trial and error.....hence the 3/8" clearance on the rear I mentioned.

And for others , these are just numbers and a starting point for "some" guidance.
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