When the time came to put the aluminum M3 control arms on my 128, I asked around for a reputable, BMW-savvy shop. Got the car back, it drove fine. It didn't stay that way.
Got the car up in the air, and this is what I found:
https://www.dropbox.com/s/jbfozp4ekz...2012.23.18.jpg
Yes, that's a nut on the upper left. It looks like maybe they stripped the threads out of the spindle when attaching the control arm, so cut the back off the threaded metal cup and went with a bolt and nut to hold the arm to the spindle.
Is it just me, or is this not a really great idea?