I have a 10 year old cheap 21 speed mountain bike that I have only ever done basic maintenance on (replacing inner tubes, tyres, brake pads, lubricating chain etc).

I have just noticed that when I pedal backwards (even slowly) the chain goes a bit loose and then starts to drive the wheel backwards. I'm just trying to find out what might be causing this, whether I can fix it myself, and whether it is ok to ride.

I have never taken anything relating to the drive mechanism apart, and don't have much knowledge about it. I have noticed that the teeth on the cogs are quite worn, but the chain doesn't usually slip off.

1 Answer 1


It's pretty normal for a bicycle with a freewheel/freehub to turn the wheel backwards a little bit when pedaling backwards a bit (i.e. if you turn the pedals backwards pretty quickly, you get some very slow backwards turning of the wheel) when the bike is in a stand/lifted in the air. You can sometimes get rid of this by servicing/replacing the freehub/freewheel.

If the wheel is turning backwards reasonably quickly when pedaling backwards, the freehub/freewheel is shot and you need a new one.

As for the chain becoming loose when backpedaling, there could be several causes:

  • Freewheel/Freehub is sticky (you'd need to service it)

  • Stiff chain (make sure all the links are flexing freely)

  • Grimed up derailleur (clean it. Jockey wheels sometimes cause this, for example)

That being said, if you're backpedalling like a maniac, most bikes will do this even if they work fine. But at slow speed backpedalling, you shouldn't really see this.

Finally, I see you didn't say you ever replaced the freewheel/cassette and chain or lubricated the chain in your maintenance for a 10 year old bike. Depending on the wear of the freewheel/cassette and chain, you may want to replace one or both. This does need a few tools (chain breaker, freewheel tool if you have a freewheel / cassette tool + chain whip), but they're relatively cheap/a very quick job for most bicycle shops.

Your bike probably has a freewheel.

  • I've added some info, as this happens even when pedalling slowly, and I have been lubricating my chain as part of my maintenance. Thanks for your suggestions, I'll see if cleaning the derailleur makes a difference and check my chain links (though I think they are ok).
    – Carasel
    Commented Jan 19, 2016 at 14:03
  • My guess is that once you clean the derailleur, put on a new freewheel and a new chain, the problems will go away (the freewheel contains the ratcheting mechanism that allows you to pedal backwards), assuming it is a 7 speed freewheel (which it likely is).
    – Batman
    Commented Jan 19, 2016 at 15:02
  • Not 100% relevant to the question but sort of is to the answer: internal hubs also spin the wheel backwards and make a ratcheting sound. Would adding this to the answer make it more useful in the future?
    – BEVR1337
    Commented Jan 19, 2016 at 15:38
  • Well, pretty much any bike will spin the wheel backwards when back pedaling. Fixies obviously do it cause they're fixed gear, and any freewheeling mechanism isn't perfect so it will do it a bit (the amount of speed in backpedaling will vary depending on setup though).
    – Batman
    Commented Jan 20, 2016 at 16:00

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