I think this one is My Tutor...
http://www.imdb.com/title/tt0085980/?ref_=fn_al_tt_1EDIT: I happened to rewatch this one last night for the first time in forever and it is DEFINITELY My Tutor that you're looking for. The friend that was strapped to the wheel was Crispin Glover and the prostitute whose boobs were used as pillows was played by Kitten Natividad. Not a bad flick, actually. Tons of gratuitous nudity, cheesy soundtrack (with the same couple of songs played over and over), several ridiculously long spandex-filled workout montages that had ZERO to do with the plot, and decent chemistry between the two leads. Not a ton of laughs to be had, but it had a decent bit of heart (and, Caren Kaye - WOW!!!)