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Discussion Starter #1
What is the minimum backspace that will fit a 68 Cougar 15 inch rims.

Thanks
 

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If I remember correctly about 3.5" it all depends on tire size and rim width though. On a 15x8 you will likely want around 4.25. The best way I know and what I used to do when doing custom wheels even in 17" is to measure the fit of the tire/wheel package. To do this know the width of the tire you want to run. Let say 235 for arguments sake. 235/25.4 is 9.25" tread width. So take a tire off, put a straight edge against the axle hub/drum extending it up into the wheel well and start your measurement from the back of that edge. get that 9.25 where you have lip clearance at the quarter panel. Factor in the width of tread you want and leave enough wheel well and lip clearance (at least 1"). Measure twice as always, write it down and check again.

I used to do this on all sorts of hot rods etc and always had great fit. You can easily get a 255 in there and likely 265/50/15. If you need more info I can pull my 68 apart and measure it. I have 18x9.5 on the rear (not by choice, leftovers from wifes 04 stang).
 

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Discussion Starter #3
If I remember correctly about 3.5" it all depends on tire size and rim width though. On a 15x8 you will likely want around 4.25. The best way I know and what I used to do when doing custom wheels even in 17" is to measure the fit of the tire/wheel package. To do this know the width of the tire you want to run. Let say 235 for arguments sake. 235/25.4 is 9.25" tread width. So take a tire off, put a straight edge against the axle hub/drum extending it up into the wheel well and start your measurement from the back of that edge. get that 9.25 where you have lip clearance at the quarter panel. Factor in the width of tread you want and leave enough wheel well and lip clearance (at least 1"). Measure twice as always, write it down and check again.

I used to do this on all sorts of hot rods etc and always had great fit. You can easily get a 255 in there and likely 265/50/15. If you need more info I can pull my 68 apart and measure it. I have 18x9.5 on the rear (not by choice, leftovers from wifes 04 stang).
Thank you this truly helps. I will keep ya posted
 

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Backspace ultimately depends on how wide the wheel and tire is. The narrower the rim, the less backspace you can get away with.

You would ideally want the mounting flange of the wheel to be centered in the wheel with respect to dish and backspace. More backspace = less dish which also affects "looks" just as much as overall fitment.

So basically you need to decide how wide the 15" rim is going to be. Then backspace can be calculated to get it to fit centered in the wheelwell.
 

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Discussion Starter #5
Thinking of 15x10 will it fit the 68 Cougar without modifying anything?
 

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I wish somebody would buy that Percy wheel fitment tool from summit/jegs and loan it to everyone who needs this info.... Wink., wink, nudge, nudge... I may need it soon
 
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