I just bought a new Trek 3900 (2007 model) and I'm just wondering how the suspension fork is adjusted. I know that there is a little knob on top that you can rotate one way or the other, but I can't really figure out what this does or how I should set it, which way is stiffer or not as stiff. The generic Trek manual I downloaded doesn't seem to cover specifics like this.
When I bought my bike recently the fork had a manual with it...perhaps you could go back to the bike shop and get that manual. Sorry I don't have a straight up answer, but I am unfamiliar with the forks on Treks.
I believe the knob is a preload which squishes down the elastimer to make the shock feel stiffer. I had a similar shock on my bike and my wife has a similar shock on her (but different brands entirely). I liked mine adjusted mostly soft and my wife liked hers adjusted full soft. It's a matter of feel, but IIRC it takes a lot of turning before you can feel the difference.
I have a trek 3900.... the fork doesnt adjust at all,... the knob is just for show lol.
it really has no effect
Crank that knob A LOT. You may notice a difference. On my wife's Judy and my old Manitou it tool a lot of turning but the shock would eventually stiffen. It would take four or five full turns before you'd notice any difference at all and only at the extremes was it at all obvious.
It's not at all like a damping setting that feels different with every 1/8th turn "click".