Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 22 Post(s)
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Quoted: 910 Post(s)
Forget the chain, check the sprocket.
If this is a fixed gear wheel, with the classic reverse threaded lockring the problem is most likely a loose sprocket. When you ride forward you tighten the sprocket. Then when you reverse torque the sprocket backs off (the sprocket stops but the wheel continues forward) until the sprocket backs into the (loose) lockring. Then when you pedal forward it slips until ti's tight, and so on.
This will continue until the lockring is loose enough to fall free and the sprocket backs off entirely when you try to stop. Or the speocket will work back and forth until something gives and you strip the threads on the hub.
The problem is very common when sprockets aren't tightened sufficiently when installed and riding pulls them forward off the lockring.
Attend to it immediately as follows. Thread the sprocket back on tight (or let it come forward by pedaling as you've been doing) then find the steepest hill around and climb it hard, or do a standing sprint. But (and this is the key) do not apply any reverse load on the pedals. Either let the bike slow gently, or use a brake, so the sprocket stays tight. Then pull off the wheel and set the lockring tightly against the sprocket.
If you do this right your problems are over, if the problem recurs repeat the process, but try for a steeper hill, or a more aggressive standing start.
Since fixed gear sprockets like spin on freewheels tighten with pedaling torque, you want to use the highest torque that you'll ever use, so that the sprocket is truly forward as far as possible before bringing the lockring against it.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
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