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Recently, when I cycled my bike the pedals would jump when I pushed down on them. I brought it to a shop who replaced the cassette, the chain, the two crank arms and probably the crankset. I have also had the rear gears replaced.

All great for about 15k, till the pedals started to jump again, when I pushed down. Thought it was sth to do with freewheeling/backpedalling when coming up to lights (as is particuarly bad when I stop/start) but that is not always the case. Also, the pedals spin when I push the bike forward - again, this is intermittent.

Have had it into the shop about 5 times, to no avail. Am lost. Bike is only about 7 years old. Anyone able to help please?!?!!

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So when you push the bike forward, the pedals/cranks turn with the wheels? It sounds like an issue inside of your rear hub, if you've replaced everything else. How tight is your chain? –  canadmos Mar 22 at 17:00
    
Is the derailleur in adjustment? Can you have someone hold up the bike and you pedal it by hand to see if the derailleur jumps? Can you feel where the jumping is occurring? –  Batman Mar 22 at 20:27
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One concrete suggestion would be to take it to a different shop. Maybe if a second pair of eyes were to look at it... –  PeteH Mar 23 at 21:39
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It sounds like a freehub/freewheel issue (the bit that lets the cassette rotate independently of the hub). When it slips, can you notice the chain slipping? It's generally quite clear if it is jumping teeth and if they're all new it sounds unlikely. The fact that backpedalling/freewheeling affect it make it even more likely to be a hub issue; same with the pushing the bike problem. –  Trengot Mar 24 at 8:45
    
What kind of bike is it? –  Booker Mar 24 at 13:23
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1 Answer 1

This sounds like there's a problem with your rear hub's freehub body (assuming you're running a cassette). The pawls get messed up sometimes and cause a jump when you're pedaling. If this is the case, you can try to replace the freehub body, which requires a bit of work. You basically have to take the axle out of the hub and get a 10mm wrench down there (most common method).

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