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I can't pinpoint the problem with my bike, but the feeling is that it suddenly feels like I have no chains, and then it comes back, like it's "skipping".

UPDATE: From the comments, I think the proper description is that it suddenly stops engaging from the freewheel. Usually it happens when I'm vigorously pedalling, or when I pedal in reverse. There's also a snapping sound when it happens. And then it returns to normal after a while.

IBG
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    Possible duplicate of If the chain/cog no longer drives the wheel, can this be fixed? – Deleted User Oct 15 '15 at 03:45
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    It's likely something is broken in you rear hub, either your freewheel or freehub, depending. The other possibility (if you are riding in below freezing temperatures) is that the grease in the freewheel is too thick for those temperatures and is stopping the pawls and such from engaging to go forward. – Deleted User Oct 15 '15 at 03:49
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    It would be a big help if you added more description: tell us about your drive train, when it happens, when it started – anything to help us visualize what your bike is like and when the problem happens. Also take a look at the related links on the right. They may have solutions and will certainly give you ideas about how to work on and clarify the problem. – dlu Oct 15 '15 at 05:18
  • I'll try. I'm new to bikes and not really familiar with the terms. – IBG Oct 15 '15 at 05:57
  • @ChrisinAK I wonder if old gummed-up grease could do this on an old, badly maintained bike. It can certainly slow down the pawls in shifters enough to cause problems, but of course the forces, speeds and exposure are different there. The solution is probably the same to grease that can't handle the cold. – Chris H Oct 15 '15 at 06:18
  • @IBG The snapping sound is bad. And the fact that it happens under high power is bad. The most likely culprit is worn pawls and/or ratchets. The snapping sound may be the pawls slipping. Each time it happens they will wear a bit more, and eventually you will probably get no engagement at all. – Deleted User Oct 15 '15 at 06:25
  • @ChrisinAK is this something I can fix? I'd try looking at it tonight. Haven't ridden the thing for about a week. – IBG Oct 15 '15 at 06:36
  • If you can reproduce the problem, try to do it while looking down and back to the back wheel. If it's the kind of problem suggested in the comments, then you should see the rear cogs turn faster than the wheel. If it's a derailleur problem you would see it and chain doing weird things. – andy256 Oct 15 '15 at 07:18
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    @IBG My stock answer is no. Almost all manufacturers do not want their freehubs or freewheel disassembled these days. Depending on your make or model, some are easier than others, but you can also make things much worse by putting back together incorrectly. I'd say see if your LBS is willing to check it out, and if not, it's new wheel time (or new freewheel if that is what you have). – Deleted User Oct 15 '15 at 23:14
  • @andy256 I tried it this weekend, and the cog does from time to time turn faster than the wheel. It then engages again and I can feel it moving the wheel, then out again. – IBG Oct 19 '15 at 00:04
  • @IBG So the answers relating to the freewheel are applicable. – andy256 Oct 19 '15 at 00:20
  • @andy256 I feel like it is. Thanks. – IBG Oct 19 '15 at 01:18

2 Answers2

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There are three possibilities that I can think of to start with:

  1. Your chain is worn and no longer fits the cogs on the cassette (or the single cog on the hub of a bike with internal gears or a single-speed bike).

    In this case the problem would usually be worse on higher gears (the smaller cogs in the rear) and under load. It probably wouldn't happen if you were pedaling gently on the flat for example.

    If you have a ruler it is fairly easy to check for chain wear. Just measure out 12 inches along the top of the chain, starting from the center of one roller. On a new chain the center of another roller will line up with the 12" mark exactly. As the chain wears it elongates and by the time that roller is at 12 1/8" the chain is worn out. Much beyond that and skipping can start. If the chain is very worn it is best to replace the chain and the cog(s).

  2. Your freewheel is malfunctioning. Two things could be wrong, there could be damage in the freewheel – either broken pawls or rounded/broken teeth, or corrosion or dried out lubricants could be causing the pawls to stick. The photo below, from A New Recyclist shows the internals of a single speed hub.

    In this case the problem would be most noticeable when you were starting to apply power, damaged pawls/teeth might also skip as power increased as well. If you have sticking pawls I would expect them to hold once they seated. Broken pawls might never seat, and broken teeth would mean that there would be small (much less than a revolution of the pedals) skips when the pawls land on damaged teeth. Sticking pawls could let you go several pedal revolutions before they catch.

    You might also be able to diagnose this by listening as you coast. The sound of the freewheel should be a very regular fast clicking as the wheel spins. Then as you start to pedal there should be a consistent firm engagement, perhaps with a bit of click after a moment of silence as the cog catches up with the hub.

    The teeth and pawls of a single-speed hub.

  3. Your shift mechanism is badly adjusted or you are shifting inaccurately.

    If the shifters are out of adjustment you may find that shifts either happen spontaneously or that you will sometimes do a "half-shift" where the side plates of the chain will land riding on the teeth – rather than on the sides of the teeth with the rollers engaging the teeth. That's not a very stable configuration and usually the chain will drop into a gear, but until it does the pedals will spin freely.

dlu
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  • I've brought it to a bike mechanic, and thanks to language barrier I did not know much about the problem. He said everything's fine with the hub though. He's saying something about grease issues though. – IBG Nov 06 '15 at 06:16
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If it happens completely quiet then it probably your freewheel (cogs) that broken and should be replaced. If you hear a skipping sound it is either your chain is too long or stretched, or (again) your freewheel is worn out.

Alexander
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