so i'm pretty new to fixed gear bikes and im still learning how everything works and these forums are great.
i've been having a problem with my fixed gear though that i'm hoping some of you can help me with. it happened first when i was doing a skid stop. i locked the cranks and began the skid but then all of a sudden i lost tension and the cranks rotated about 45 degrees before locking in again. it felt like maybe the cog slipped or something. now it happens a lot, like if i stand up to get the bike moving from a stop the gear will slip and the cranks will quickly drop about 45 degrees. whats the problem here and how can i fix it?
your cog is slipping. this probably happened because it or the lockring was not initially tightened enough. it may have already stripped the threads - careful. don't ride it until you get it fixed; maybe you need to take it to a bike shop. or, do it yourself - remove the lockring and remove the cog. inspect the threads - make sure they look intact. if they look chewed, removed, stripped, flattened, or anything ****ed up, then you're going to need a new hub if it's not a fixed/fixed fduplex style hub.
if the threads are okay, grease the threads and put the cog back on - you can tighten it using the "rotafix" method (do a search for the link for how exactly to do it - it's using your chain as a stand-in for a chainwhip). then, install your lockring (grease the threads!) and tighten the **** out of it. then go for a ride up a hill using only forward pressure - no skidding, no backpressure. really mash down hard to make sure the cog is on as hard as it can go, then re-tighten the lockring.
it seems that a lot of factory trackhubs come from the dealers with improperly assembled cog/lockrings, and don't hold when the rider starts skipping and skidding - hence the slipping. but, if you haven't stripped the threads, there's no reason to worry - it's a quick fix.
i have a fixed/single speed flip flop hub. is it okay to ride it on the single speed side for now?
oh absolutely. there's nothing wrong with that side.
i've had a cog do plenty of slipping without stripping the threads, but every time it moves it's possible for it to chew the threads to uselessness. so ride the freewheel side to the bike shop and get that fixed side fixed.