chrisguzman

Guys, I have a question in regards to the rear end on my 66 mustang. Currently I have an 8" measuring 52.25". My buddy has an entire 9" set up that measures 54.25" that came out of a 67' Mustang and was wondering if that would work in my 66'. I know the spring mounts line up but could not find any info on whether or not that 1" on each side "HAS" to be cut or if I could do a 1" back spacing on the rear wheels. If it does work can I still get decent size wheels in the back? Thanks for the help guys.

dodgestang

If you simply use wheels with a different backspacing it works just fine.

For example...

if a 17x8 with 4.75 fits stock

then

a 17x8 with 5.75 would fit the same way with your 1 inch wider rear

lumpyidle

I used this exact setup in my '65 with no clearance issues, but that all depends on the tire/wheel your using. I was running 205-60 R14 tires. So if your not running big rims or tires (stock for instance) you won't see any problems. I ran some other wheels in the back for a little bit while I was converting from 4 lug to 5, I changed the rear end before changing over the front, ran it like that for about 6 months or so on a pair of '90something mustang V6 rims, (the ugly 3 spoke with the little 3 oblong holes in it) I think they were 15x7"? Maybe 16", I don't remember, with the stock tires which are pretty low profile by comparison to the old cars, I had to replace the studs with longer ones because the stock lug bolts weren't long enough to go through the stock thick aluminum ford rims. But with the wider rear-end and the different off-set of the more modern rims they fit perfectly under the car, with plenty of clearance both inside the wheel-well and the fender lip. Never had to roll the fenders, hate when people do that. Anyways, hope this helps! Oh, remember to save the parking brake cables out of the original rear-end, compare them to the new one and switch them out if they are different. But yes with the non-stock (for '66) backspacing you can get the size you want under there. Just keep in mind that you won't be able to rotate your tires if you use stock offset rims upfront. Or you could use a spacer on the front wheel, which probably means you'll have to put longer studs in the front rotors/hubs too, which I wouldn't do, just doesn't seem like it would be too good for the bearings to me.

67t5ponycoupe

You will also need to run the U-bolts and shock plates from the 67. The housing tube is bigger on the 67 than on the 66.

66$tang

i did the same thing in my 66 and it had no prob just needed different backspacing

chrisguzman

Right on, thanks for the help guys.

nba1341

Why would you want MORE backspacing if the rear end is enlarged by 2 inches. Wouldnt that make the wheels stick out 2 inches more versus 3.75 backspacing which would make it equal?

dodgestang

No.

https://www.rsracing.com/tech-wheel.html

A modern mustang rim (something like a 2001 17 inch bullitt) has approx 5.75 (5.72 is the exact IIRC) backspacing and generally can not be run on the car without a 1 inch spacer because it sits too far into the wheel well and rubs on the inside of wheel wells. The 1 inch spacer changes the backspacing to 4.75 by pushing the wheel out 1 inch. If you put a rear in that is one inch wider and then decrease your backspacing by one inch as you are recommending your wheel will now sit out 2 inches further that it would with the stock rear and a correct backspaced wheel.