I realize conventional wisdom is to move entire front S4 suspension to upgrade to S4 brakes on an 82-86 car, but what would be the specific effects of just using S4 spindles? I thought I read somewhere on here someone doing just this, but cannot find it.

To my untrained and untested (re suspension geometry) eyes , it looks like it will work.

I have S4 brakes, rotors, spindles and lines.

 

As I understand it, if you have and plan on keeping ABS, you will need to use S4 rear spindles and the S4 ABS brain as well.
The rear spindles to keep the tooth count synced up and the brain to tie it all together.

 

Thanks Ken. No ABS on my 85. I wondered if using early arms with S4 spindles would negatively effect suspension geometry.

 

yes it will.
the early suspension should only be used with the early spindles.
If your looking to fit bigger S4 brakes follow Kens ^^^^ thread about where he bought the adapters to fit the S4 calipers

 

Thanks MrMerlin. Given your defining tip, I will be swapping the spindles off of the 80 and calling 928I for adapters.

 

This is an easy swap out with the right parts
IE caliper adapters, good luck!

 

Thanks Stan. A nice PM from Mr.Rudd has me all sorted.

After I get my centering spring situation fixed, I will get moving on the upgraded brakes.

 

The early upper and lower A-arms are longer.. and using an early lower and late upper gives you about 5-6 degrees of negative camber with an S spindle which I then shim out the upper arm to have about a minus 3 1/2 to run on the track.