I ran 215/60R15's with the stock rims on my 300E for years and years without any problems. Rubbing wasn't an issue, and while the tire sidewalls do seem a bit bulgy for the narrow rim, the actual tread width seems appropriate for the car - the stock 195's are way too narrow IMHO.

Just recently, I transitioned to Dunlop SP5000's in a 205/60R15 size, and the three things I noticed most were:

-slightly reduced steering effort.
-improved dry traction.
-reduced wet grip. (this one I can't figure out, although I do drive a bit more aggressively than I used to..)

anthony