Aptly named, the Boa stays tight. I have had both my mountain bike and my road bike on at speeds in excess of 80mph on the highway with heavy side winds and the bikes stay solid (although I would recommend strapping them down as tight as you can). I have also used the Thule Velo Vise Tray, but this rack system is way tighter!!! Works equally well on my Thule square crossbar. The only inconvenience I have come across is that you have to move your crossbars to adjust for different bike lengths so I would recommend this rack only if you are carrying the same bike(s) all the times...although the rear strap does adjust slightly if you need to carry bikes with varying wheel spacing (for me, a mountain bike and a road bike). Good rack, easy to use, and not bulky like a tray.