is the rubbing noise coming from within the steering wheel itself or the steering machanicals down in the engine bay/suspension?
i also have a 2002 and have a rubbing noise in the steering wheel and i believe it is the ribbon cable for the airbag and controls. it is an absolutely royal PITA to get out and from my experience there isn't much you can do about it. i put a bunch of silicon paste in there but it didn't do that much.
maybe BMW has improved the part and replacing it would cure the problem.