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This morning during my morning commute I had an unintended lesson in fixie skidding: I dropped the chain, it got stuck between the cog and the hub and locked the wheel. I'm not sure where that skill came from, but I managed to come to a controlled stop without falling, crashing into the curb, or swerving into traffic. Scary, I must admit.

I was only a few blocks from work, so after a good deal of not-so-gentle pulling I managed to dislodge the chain, get it on the chainring and cog and get going. I did notice during the short remainder of the trip that if I applied back pressure on the pedals, the cog was no longer being held in place by the lockring. Not that I understand how that could have happened, but other than that and the terrible skid mark on the tire, nothing else felt wrong.

Once I get home I will get a new tire on (kids, put brakes on your fixies, if only for financial reasons!), tighten the cog and lockring, check them for damage, measure the chain to see if it needs replacement, and make sure it sits a little more taut.

Am I missing anything? Not sure if I should be looking at anything on the hub, spokes or elsewhere...

Update I spent some time with my back wheel today. The spokes are all dented and scratched, but the wheel is holding up well. I took the lockring and cog off, and they both looked fine, same with the threads. After cleaning them up and putting some grease on the threads, I put the cog back in and tightened it with no problems, but when I was tightening the lockring it disintegrated: it obviously cracked during the chain jam, which allowed it to move out without stripping the threads. I am riding on the flop side of the wheel now, which has made for an interesting discovery of forgotten feelings. I had been thinking of taking a tooth off my back cog for some time, so I'll just go ahead an order the whole pack: cog, lockring and chain.

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There's a vague possibility that you stripped the lockring. And more than a vague possibility that you've bent the cog or ring. Also, the wheel may have been knocked out of true. –  Daniel R Hicks Feb 5 '13 at 1:52
    
Make sure you recenter your chainring and check those chainring bolts. –  WTHarper Feb 5 '13 at 2:10
    
Check your hub. Make sure the threads are not stripped where are you screw on the Lockring. –  Benzo Feb 5 '13 at 23:08
    
Also, make sure to grease the faces of your cog and lock ring where they touch one another, this helps prevent the cog from engaging the locking and loosening it. Give the lock bring a good re-tightening after the first ride. –  Benzo Feb 5 '13 at 23:10
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up vote 2 down vote accepted

I would certainly give a lot of attention to the chainring and lockring. One question that I think you need to answer is whether the lockring was loose before the incident or did the chain jamming the cog cause the lockring to come adrift. Then you need to consider whether the lockring loosened naturally, i.e. did it turn along the thread, or was it forced sideways?

Do you tend to use a rear brake? From the question I get the impression you don't. (This isn't a criticism - I don't have a rear brake on my fixed, either.)

If you use back pressure a lot when slowing and the lockring had been a little loose (when was the last time you checked it?) then it might be that that was what helped contribute to the jump - this is probably the best case for you, certainly the case with the least likelihood of damage beyond the tyre's flat spot.

If you're sure that the lockring and cog had been tight before the incident, then I would really give the threads a careful review because you might have stripped them and caused some lateral damage.

Given the jam, I would certainly be looking at the spokes: go round the wheel, both sides, just trying to gently flex each spoke, they should each hold firm; listen for creaks too. It also never hurts to pop the bike in a stand and just run the wheel round a few revolutions and watch its line - even if the spokes are all firm, you might see a little wobble.

And if you're really thorough, go over the chain and check for bent links (and while you're at it, give it a good wipe and a lube, you can't do that enough).

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