I am thinking of buying a bike rack from small independent USA company Bird Automotive for my 2006 Z4 roadster. The rack slots into two receiver pipes permanently attached to the chassis under the rear bumper, so doesn't touch the body of the car at all. It's quite expensive at around £480 imported cost, but looks like a great bike carrying solution. Check it out at birdautomotive.com. Does anyone else have one if these?