I just purchased the 400XTR Rapid Aero bars and foot pack, along with the Echelon Bike Carriers (2) and the XAdapt9 kit. The installation was quite simple, although setting it up the first time took a little while, which is to be expected. As I drove around with the Echelon Bike Carriers on the car, I noticed a rattling sound coming from the area where the XAdapt9 kit fastens to the Echelon bike carrier (on the rear Aero bar). The problem is that the XAdapt9 fastener plate does not fit as tightly as it should inside the bottom of the Echelon bike carrier - so it rattles from left to right and a little up and down as well. However, I found a solution that has worked great! I went to my local Home Depot and (in the aisle where all the nuts and bolts are kept) found a 2" diameter rubber washer (very thin) with a small hole in the middle. I removed the fastener plate from the Echelon carrier and then stretched the hole of the rubber washer around the two prongs that fit up and inside the underside of the Echelon carrier - it's snug, but it does work. When I reinserted the fastener plate (now with the rubber washer attached) into the underside of the Echelon carrier, it was a little difficult getting it started, but once it found the track, I could slide it all the way up to where it fastens to the rear Aero bar. I also placed a little piece of the rubber strip (included with the Aero bars) where the fastener plate sits on top of the Aero bar. The result is that I have eliminated the rattle and the problem is solved! Hope this helps if you experience the same problem I had. Rack on!
2009 Mini Cooper S