Bicycle Mechanics - weird problem?
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08-02-12, 07:50 PM
i bought a single speed bike and it was my first time riding and everytime i try to pedal or brake too hard the pedals slide a bit and then it continues in a circular motion. im not sure what the problem is
08-02-12, 08:00 PM
This is a single speed, not a fixed gear correct? From your (rather vague) description it sounds like the freewheel mechanism isn't working properly. If the bike is new, take it back to the selling dealer for repair or warranty work. If you bought it used take it to a dealer to determine what the problem really is.
08-02-12, 08:10 PM
it's a fixed gear. basically when i pedal or brake hard it doesn't catch on and the wheel doesn't spin more or brake like it's suppose to
08-02-12, 08:44 PM
Just to clarify, you have a fixed gear bike and when you pedal hard or put reverse pressure on the pedals, the chain slips. The usual suspect is a loose chain probably caused by a chainring that's off center, causing the chain to tighten and loosen as you pedal or you may have a worn cog and/or chainring (is your bike actually new or just new to you?) You may also have a cog chain mismatch; cogs are 1/8" and chain is 3/32. Lastly is the remote (and dangerous) possibility that you are using a tensioner with your fixed gear, which will cause the problem you describe and eventually kill you..
08-02-12, 08:53 PM
it's a new bike. its a motobecane track back from bikesdirect.
08-02-12, 08:54 PM
the info on the parts is there so does that eliminate the mismatch problem?
08-02-12, 09:18 PM
Assuming it's assembled correctly (always a question with BD) I expect the chain tension is incorrect.
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.
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