Relatively new car wash near SouthRiding area said their rails accommodate up to 13 inches, that's about 330mm. Meaning, there is about 1.5 centimeter of room to make mistake, that's about your thumb fingernail width. I wonder if 13 inches is pretty norm since this place seems to have all the latest.

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2011 X3 35i
2008 X5 4.8i
2003 330xi -sold-
2001 X5 4.4i -sold-
2001 M5 -sold-
2001 M Roadster (SCed, Highly modified) -sold-
2000 M Roadster -sold-
1995 325is -sold-