I have S03s in size 225/50 r 16s on my SLK and it is great. The diameter appears within norm.

Generally, S03s are slightly wider than other brands so if your car barely fits (width-wise) in your current setup, you may have rubbing problems against the fender with the S03s.

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'00 E430 White / Gray w/ Xenons
Brabus 19'' Monoblock V, 2 piece
H&R Sport Springs

'03 Porsche Carrera Coupe, Silver / Blk, 6-speed
Xenon, Sport Suspension, Bose, GT-3 Side Skirts . . .