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shep76

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I measured and calculated the best backspace for my fronts are 15x7 with 4.5 BS. Rears 15x8 with similar or a little more BS. But looking for wheels it’s really tough to find 4.5” BS. Even the super popular cragars only give 4.1 BS. I see tons of pics of darts with those SS cragars, where did they find them with that BS? Any ideas?

69 Dart, big bolt pattern
 
Hmmm. Guess not. Cragar won't do custom offsets anymore. American racing or the weld prostars seem to be the only option. 15X7 with a 4.5" offset is a rare breed... I have 4.1 offset right now but I feel like they stick out to far.
 
I thought 4.25 was a pretty common BS.

Seems like I've measured that lots of times.
 
YY1 said:
I thought 4.25 was a pretty common BS.

Seems like I've measured that lots of times.
Click to expand...
With cragars the most backspace I could find with our bolt pattern is 4.1. I have 4.1 right now. It's ok but another 1/2" would be better. When I read through this site most people were reccomending 4.5" BS as well. The calc I used said 4.5 too. I'll keep looking. Thank you
 
Interesting- I just looked up Moapr 15x7 rallye wheel backspace and got multiple hits that it's 4.25.

You want more? IE the "dish" on the front of the wheel is shallower?
 
Factory BBP 15x7's had a 4.25" backspace, but the factory tires were pretty narrow. If you want to add more tire width you can use a little additional backspace. Not a lot with a 15" rim though because the rim will hit the suspension/brakes. 4.5" of backspace is pretty much the maximum for a 15" rim.

A 225/60/15 is about the widest you can go on the front with a 15x7 and 4.25" of backspace. Decrease that down to 4.1" and some cars would probably need to stick with a 215. With a 4.5" backspace you might be able to sneak a 235/60/15 on a lot of cars, or just make 225's a lot easier and give some room for a lower ride height.
 
I currently have some trash wheels and tires on it 205/60/15 with 15x7 I think. Measured the backspace at 4 1/8. They seem like they stick out to far….however after looking again I think I need to replace the ball joints first, the wheels are really cockeyed in there. Thank you for the factory specs, that’s reassuring.
 
shep76 said:
I measured and calculated the best backspace for my fronts are 15x7 with 4.5 BS. Rears 15x8 with similar or a little more BS. But looking for wheels it’s really tough to find 4.5” BS. Even the super popular cragars only give 4.1 BS. I see tons of pics of darts with those SS cragars, where did they find them with that BS? Any ideas?

69 Dart, big bolt pattern
Click to expand...
I see you have a 69 with big bolt pattern. How did that happen?
 
shep76 said:
The fronts are drilled. The rear is 8.25 rear end. I didn’t do it so the quality of the work is yet to be seen….
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You should measure carefully in case the rear end is a different dimension than what the car was built with.
 
72bluNblu said:
A 225/60/15 is about the widest you can go on the front with a 15x7 and 4.25" of backspace.
Click to expand...
I’m fine with 215 or even 205. What surprised me was the SS cragar have a max backspace of 4.1. They seem to be very popular on these abodies so I figured finding them in 4.25 or 4.5 would be no problem. I think once I correct the ball joints the 4.1 will be ok. I did measure lots of times. I used this formula I - [(I+O -W -1)\2] where I and O are the distance from the mounting surface to the first obstruction. W is rim width.
 
shep76 said:
I’m fine with 215 or even 205. What surprised me was the SS cragar have a max backspace of 4.1. They seem to be very popular on these abodies so I figured finding them in 4.25 or 4.5 would be no problem. I think once I correct the ball joints the 4.1 will be ok. I did measure lots of times. I used this formula I - [(I+O -W -1)\2] where I and O are the distance from the mounting surface to the first obstruction. W is rim width.
Click to expand...

With a 205 they'd clear fine, and yeah a 215 would probably be ok for most cars.

I don't think it's all that surprising, a lot of the 15" rims also fit vintage Fords and they don't need as much backspace. And the cars that run Cragars usually aren't the ones looking to fit really wide front tires, so a 15x7" with 4.1" of backspace would sell fine. It's not easy to find any rims in a 15x7 with 4.5" of backspace, 4.25" is about the best you do most of the time.
 
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