Are you lowered on springs or coilovers? If coilovers, did you adjust your camber? What size spacers are you using? The fact 235 has worked for others leads me to believe two things...
1) If you're on coilovers, you adjusted your camber and that is contributing to the tire not clearing the fender.
2) If simply lowered, you must have the wrong offset. If you need spacers, then try another size. Spacers are availabe anywhere from 3mm and up. I would first try various spacer sizes before exchanging the tires for new ones.
As a last note, please realize there is a small metal protrusion in the front wheel well that may be causing contact. You can read about it here:
http://www.mbworld.org/forums/showth...ght=protrusion