What's this screw for?
 

Socket-head cap screws on the bottoms of my forks. What they do? My forks are clunking and I don't see anything wrong with them. Could these be drain plugs?
I'm wondering because they are on my commuter bike which stays outside. Good chance there's water in there and it could be frozen.
http://bikeforums.net/attachment.php...hmentid=428284

It depends on the fork but it's either an adjustment (doubtful) or used to disassemble the fork.

Thread starters.

Actually they may hold the suspension mechanism home, and prevent the upper assembly from being pulled totally out of the lower one.

Whether it's safe to remove them temporarily to possibly drain the struts depends on the specific fork. If you have a spring or elastomer fork, it's probably OK, as long as you replace them, but I've seen some designs that call for a super long wrench from the top to hold the mating part.

See if you can find an exploded view of your specific fork, then decide if you want to take it apart.