1) The diameter of any tire, if it's the same (+/- 4%) will work.
So, you can go to a 55 or 50 or if you're really nits, 45 series tire.
2) The width of the rim will dictate how wide you can go.
You could go wider but it starts getting silly. I wouldn't go more than 235.
Once more with feeling:
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
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