I don't recommend the tow hitch mounted bike racks. I know the access is easier because of the height but they're more likely to damage your car contrary to popular belief. Everyone is afraid to ruin their roof when mounting stuff. The x5 has the roof rails already so a bar mount system from Thule isn't expensive because its universal. Thule makes the BMW branded racks and hardware. Also, tow hitch bike racks put stress on the bike frame because they don't mount by the wheels or the fork.

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2004 BMW M3 Individual
2009 BMW E70 X5 35d
2011 BMW E70 X5 35d - Totaled
2009 BMW M3 E90 - SOLD
2006 E53 X5 4.8iS - SOLD
2002 E46 M3 Convertible - SOLD
2006 E46 M3 ZCP - SOLD
2011 E70 X5 35d - SOLD
2000 E39 ///M5 - SOLD
2003 E53 X5 4.6iS - SOLD
2006 E83 X3 3.0i MSport - SOLD
2000 E46 323Ci - SOLD