Need help with Mercedes rims sizes

[Casey]

I am considering purchasing a C320 or E320 for my wife, and I am wondering what are the largest size wheels I can put on w/o making any other changes to the car(18", 19"??). I have seen a couple sets of BBS wheels on these cars and really like the look, but I cannot remember what size they were.
Any help is appreciated!
Thanks!

Casey

Oops! Just noticed I posted this in the wrong section! Sorry!