Originally Posted by samundsen
It's adjustable, but as far as I know, not with an allen head, it's just a plastic adjuster that surrounds the seatpost. I have tightened it as far as it can go. My bike is a Specialized Expedition Elite 2002.
Pull the seatpost out of the frame-you will find an allen head recess at its base (if memory serves, it's a 6 mm). Tightening that will increase the preload on the spring in the seatpost.