I wouldn't have a problem using stainless wheel nuts on a car. In fact, I made up a set for a Group A 205 GTI I once ran with absolutely no problems at all and that was a car which was subjected to considerable use/abuse!
I'd draw the line at making the wheel studs from stainless though. Firstly, the elastcity/stretch properties highlighted by Cheshire David. Secondly, unless adequately lubricated on assembly, there is the potential for the nut and stud to weld themselves together!
Arwyn
