Not air, but water, mud and debris filling the scoop.
Dave, I have chain steering on my commuter bike. I went to push rod steering on some newer bikes. Chain has unlimited steering, its hard to get more than +/- 35 degrees without the rod hitting something, but its better for narrow Q. I am in the process of designing-building a new bike I want to try a over the shoulder space frame.
http://www.crazyguyonabike.com/doc/?...27&v=2i#182576