I had 20's on my last X5 and to be honest, i never had any luck with balancing outside BMW dealer. THey have the correct machine for these wheels and they were the only shop to fix the vibrations, shimmy in the wheel.

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2013 X5 5.0 - M Sport, M Performance, Black Saphire, Black Nevada.
Previous -2011 5.0 Msport Titanium Silver, 2008 X5 4.8 BS, sport, 214's, black Nappa.