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Discussion Starter #1
I have a 67 Fastback with Granada spindles on the front and a 9-inch out of "what I don't know" in the back. I have American Racing torque Thrust D 15 x 7 3.76 backspace -6 mm offset from the spec sheet for that wheel. I have BFG 225 60 r15 all the way around. I did have to roll the fenders originally. I'm thinking the backspace 3.76 is the reason why I had to roll the fenders. I want to replace the wheels not the tires. I have stock upper control arms I did not drop them but I might want to in the future. So I'm thinking 15 x 7 or 15 x 8 and what should the backspace be, most wheels are either four or four and a half. I'm not sure what the offset should be. Any help would be appreciated.
 

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I have a 67 Fastback with Granada spindles on the front and a 9-inch out of "what I don't know" in the back. I have American Racing torque Thrust D 15 x 7 3.76 backspace -6 mm offset from the spec sheet for that wheel. I have BFG 225 60 r15 all the way around. I did have to roll the fenders originally. I'm thinking the backspace 3.76 is the reason why I had to roll the fenders. I want to replace the wheels not the tires. I have stock upper control arms I did not drop them but I might want to in the future. So I'm thinking 15 x 7 or 15 x 8 and what should the backspace be, most wheels are either four or four and a half. I'm not sure what the offset should be. Any help would be appreciated.
The optimum original factory backspacing for your car with a 15x7 wheel is 4.25" (+6 offset). For the 15x8 it's 4.50" b.s. (0 offset). If you aren't aware of it, backspacing and offset are merely two different ways of expressing the same thing. I don't know how much (if at all) having Granada spindles up front changes things, but someone here is sure to. It would behoove you to know the distance between mounting surfaces on your rear end too.
 

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Discussion Starter #3
Thanks for your comment. From what I read the Granada spindles don't make any difference. As for my rear axle, the spring perches were all just where they were supposed to be and the backing plates bolted right up so I think it's just what it supposed to be. I didn't know that about the 6 + m m + 4 and a quarter being the same thing so that was new and good information thanks.
 

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Correct Granada spindles don't affect backspace/offset requirements
Just because the axle had the spring mounts in the right location doesn't mean the over all width is right
 

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Guaranteed anything over a 215 on those wheels will rub up front. Can’t speak for the rear since you probably don’t know the actual width of the rear. However, I’d suspect 215 on TTD’s might be your max.
 

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Guaranteed anything over a 215 on those wheels will rub up front.
You bring up an interesting point. How low the front end is and how much camber is dialed into the alignment notwithstanding, many aftermarket 15x7 wheels (many Cragar for example) have a backspacing that isn't terrific for these cars despite being sold/marketed for them by numerous vendors. Something easily missed is that a 15x8 with 4.5" b.s. will fit a larger tire better up front than a 15x7 will when the optimum b.s. is off by a whopping 1/2" or so. Even with the "Shelby Drop" and 1/2 of a coil cut from each GT spring, I run with 15x8's up there with no rubbing. Two of my eight wheels are15x7 Cragars with the not optimum backspacing. I put smaller tires on them to serve as spares.
739680
 

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You bring up an interesting point. How low the front end is and how much camber is dialed into the alignment notwithstanding, many aftermarket 15x7 wheels (many Cragar for example) have a backspacing that isn't terrific for these cars despite being sold/marketed for them by numerous vendors. Something easily missed is that a 15x8 with 4.5" b.s. will fit a larger tire better up front than a 15x7 will when the optimum b.s. is off by a whopping 1/2" or so. Even with the "Shelby Drop" and 1/2 of a coil cut from each GT spring, I run with 15x8's up there with no rubbing. Two of my eight wheels are15x7 Cragars with the not optimum backspacing. I put smaller tires on them to serve as spares. View attachment 739680
that is less likely to work as well on a 65/66. the fender/wheelhouse is smaller
 

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Discussion Starter #8
The wheels that I want to buy are 15 X7 and have a 4in backspace the tires that I'm running are 225 60 r15 the fenders are rolled in the front and I've never had a clearance issue in the back. Before I send some stranger $1,200 for a new set of wheels do you think I can get away with it?
 

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FWIW on my 65 without Shelby/Arning drop, Mustangs Plus 600#/KYB’s/14”x6.5”Cragar ten hole rims (could have had more backspacing) with 235/60/14 BFGs on Granada spindles.

A few years ago I performed Shelby/Arning 1” drop while rebuilding front end.
I kick myself in the butt for not doing it 20+ years ago. Drives so much better too.

I was looking at prices for 14” & 15” tires and I was disgusted with the prices. Especially with 16”-18” tires and even better traction.
Needless to say, I picked up some good used 18”x7.5” rims ( I’m using a 1” wheel spacer) and have 235/40/18 Pirellis (they seem to run a little narrow) with way better traction for winding roads.
No fenders are rolled either.
TMI??
Seriously though, hope this helps!
 

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Backspacing with 1” spacers on 18” is 4.75” with 235/40/18 Pirelli
 

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The wheels that I want to buy are 15 X7 and have a 4in backspace the tires that I'm running are 225 60 r15 the fenders are rolled in the front and I've never had a clearance issue in the back. Before I send some stranger $1,200 for a new set of wheels do you think I can get away with it?
Yes, given the rolled fenders and a proper amount of negative camber in the alignment. What wheels are they? Post a pic! Also, if you do the UCA mod it'll lower your front end 5/8" further so take that into account. You'll notice the improved handling immediately. I would recommend a 1" anti-sway bar and an export brace as well if you don't already have 'em. You don't need to spend gobs of cash to have a really nice handling front suspension on these cars.
 

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Discussion Starter #13
Yes to export brace and 1 inch anti-sway bar. I drilled the holes for the drop 15 years ago tried it tires rubbed and put it back and then rolled the fenders. I had AC springs and it was too high and got non AC and it's been fine ever since. I really want these wheels. If a 4 inch backspace won't work I will scrap the whole plan and leave it alone.
 

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Discussion Starter #15
I found this nifty offset calculator. It said the tire will be 1/4 inch farther from the fender and 1/4 inch closer to the suspension and frame. Am I reading this correctly?
On the car now 22560r15 tire 15x7 -6mm offset wheel, Want to have 22560r15 tire 15x7 0mm offset wheel. I will have to check the space I have to the UCA and to the frame with the wheels turned lock to lock. I think I feel better about this!
 

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I found this nifty offset calculator. It said the tire will be 1/4 inch farther from the fender and 1/4 inch closer to the suspension and frame. Am I reading this correctly?
Yes, compared to what you had before. Still not optimal but a full halfway step in the right direction towards it. With the front fenders rolled and some negative camber you should be good to go. They should fit in back no problem. Good looking wheel, different than most we see for sure.
 

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Definitely a great looking wheel. Can you provide specs on the 15x7. And 15x8 wheels? Including offset or actual backspacing? The cragars i had, as mentioned, didn’t have ideal backspacing for my 65. “Backspacing is your friend”. They could have used another 1/2” of backspacing. I’ll take a look at my cragars and find out that information.

Sounds like you haven’t purchased yet.

If it’s at a local shop, would you be able to fit a rim on the front BEFORE mounting a tire to see where the wheel ends up to fender?
 

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Discussion Starter #18
I found this nifty offset calculator. It said the tire will be 1/4 inch farther from the fender and 1/4 inch closer to the spension and frame.
 
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