I recently upgraded my rims to some Velocity B43s and since the switch I've had my cog come loose a few times. I'm riding the Origin8 TorqLite 17t cog right now with my original lockring from my first rims that come standard on the Langster, pretty sure they were some AlexRims or something like that. The slip doesn't happen all the time, just every once in a while when I'm backpedaling to come to a stop, not even when I skid. I cranked both down as tight as I could get them but it still happens now and then. Anyone ever had this prob? I just ordered a new cog and 2 new lockrings to try out (an Origin8 and a Shimano) so hopefully the combo of the new cog and lockring works, but if anyone has ever had this prob and has any advice or fixes I'm definitely down to hear them. Thanks.

You might have stripped your hub cause the cog and lockring weren't tight.

My buddy had this problem, but it was because he didn't tighten the lockring enough.

This is how I tighten the cog/lockring, worked well for me. Do this and also check your threads for damage. You must have a good quality lockring wrench for this. I use a Hozan myself.
1) with wheel off thread on cog until hand tight. Thread lockring on but not all the way.
2) mount wheel on bike with correct chain tension. Then pedal real hard to create the torque necessary to fully tighten the cog
3) with the cog fully tightened on the bike, tighten the lockring on until handtight, then take a lockring wrench and tighten all the way. Use the whole length of the wrench for leverage.

rotafix?

you can tighten your cog and lockring without any new tools if you just need to do it this once. use the rotafix method, which involves no tools, just look it up on youtube or something. anf then to tighten your lockring, not recomended but can be done safely, use a flat head screwdriver and a hammer just tapping the notches until it's tight enough.

but if you plan on doing this more than once i recommend getting a chainwhip and lockring tool.

Only if you want:
- A chance at stripping your hub
- A chance of not ever getting the cog off


Properly installing the cog and lockring is the way to go.

Surprised that I've seen a couple of these threads recently. I would think its basic knowledge for fixed gears to know that if your cog is slipping, its just plain not tight enough. Isn't that a prerequisite to putting together a fixed gear? Don't get me wrong, I'm not calling anyone an idiot or anything because I've stripped a hub myself, but it was because I didnt have a chainwhip yet and the bike shop I took it too didnt tighten it for crap.

A new cog and lockring wont help you. Its rare that they are the ones with stripped threads unless theyre truly generic crap and sadly, if anything is stripped, its your hub.

If your hub is stripped, start with new hub, reputable brand cog and lockring and take it down to a good shop to have them install it. If you're going to be changing these parts out by yourself in the future by a chainwhip and lockring spanner, or a combo tool.

well.. agreed. But my puny girl muscles makes the usual chainwhip method kinda loose. The rotafix method is okay for me since I'm not really capable (and am also careful) to tighten it to the point of stripping hubs.
Everytime in the rare occasion that some guy tightens my wheel I always have to put a wrench and step on it with my body weight to take it off.

This is how I usually do it on my bikes too. Never had a problem with anything slipping or being able to remove the cog.

Around here we refer to it as the "ghettofix method".

This is how I usually install my cog/lockring too which is why it was so weird to me that this was happening. I'm not some clueless rider that doesn't know how to install a cog and lockring, I've been a bike mechanic for 6+ years now and never had a prob until my new rims, it was just really weird to me because the cog and lockring are supposed to counteract each other if the cog slips, the ring is supposed to tighten or catch it, but both were moving freely once in a while. I took off the cog, replaced it with a new one and put a shimano dura ace lockring on (seems a lot more solid than my old one), so we'll see how it goes. I also checked the threads and they are fine, so maybe I just had a bad cog/ring combo, we shall see. Thanks for all the input though.

How often are your checking your cog to make sure it is tight? Swing by Continuum Cycles on Avenue B and they will put it on nice and proper and won't require checking it.