hey i have 225/40zr17 in the front and 235/40zr17 in the back, the rims are from a slk 2003 and those are 9" wide, i do a little little modification into the front fenders and never rubs!
the modification was bent the internal fender panel to the max, and thats all

 

Are the rear fenders of the e500 also wider than the standard W124?