Hey, I'm new to the world of Fixed gear and singlespeed bicycles (and the forum-I posted an introduction thread a little while ago). I have a new Jamis Beatnik that I'm currently running with a freewheel, and although I really like it, I've noticed a bit of a problem with the chain. after every ride I take on this bike, it seems like I have to flip the bike over and re-tension the chain, as it seems to become slack over a course of time. My question is, what could the causes of this problem be, and how can I fix them? The bolts on either side of the dropouts are tight enough so that the wheel doesn't slip, so I don't think thats the problem. Insight would be much obliged.