Pedal fallen off (Bosch motor)

Discussion in 'Technical & FAQ' started by The Bear, Mar 13, 2018.

  1. The Bear

    The Bear Pedelecer

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    My pedal and arm fell off my Cube Reaction Race ebike today whilst cycling to work.

    I managed to retrieve it but the nut or whatever holds it on is missing. All I’m left with is the pedal assembly and the exposed splined shaft of the crank in the motor.

    What part would I need to fit it back on, and what tool would I need please?
     
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  2. It's a crank bolt that you tighten with a normal allen key. I'm not sure of the size of the thread on that one, but any cycle shop should be able to remove the one on the other side to compare and replace. Try Halfords if you have one nearby. they're normally pretty good with help when you're broken down.
     
  3. The Bear

    The Bear Pedelecer

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    Thanks

    I pass the shop I bought the bike from on my cycle home, albeit I shall have to push the bike to them!

    Im just hoping that the splined shaft hasn’t worn.
     
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  4. It's hardened steel. The pedal arm could wear, though unlikely, but not the shaft, so nothing to worry about.
     
  5. soundwave

    soundwave Pedelecer

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  6. Nealh

    Nealh Pedelecer

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    This is where a throttle enabled bike comes in handy in a get you out of trouble scenario.
     
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  7. marwigan

    marwigan Finding my (electric) wheels

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    Common problem; let me guess tis the left hand pedal/arm.

    happened a lot with my panasonic motor Giants etc too. It;s because the anticlockwise motion of the left side is always potentially 'trying to undo' itself.
    Solution is to tighten crank bolt blooming hard perhaps with a drop of superglue on the bolt [clean wi meths first].
    Helps to have a tightening tool with you as you will feel a 'give' and waggle for a mile or two before it drops off in the road with a clang. Nothing then to stop the fixing bolt disappearing though mine crank arms are fixed wi nuts under a plastic cover so at least they don't go walkabout
     
  8. The Bear

    The Bear Pedelecer

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    Correct, it is the left one.
     
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  9. The Bear

    The Bear Pedelecer

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    Took the bike back to the shop I bought it from today, they have ordered a crank bolt for me to collect next week. Im not confident of getting it free of charge, I got the impression I would have to pay for it despite the bike being only 4 months old. Ive no idea how much it will cost, but I would have thought they would replace it free for me a a gesture. I shall wait and see.

    [​IMG]
     
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  10. flecc

    flecc Member

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    When the first Bosch equipped bikes were released, the left hand crank arm falling off was their first reported problem for many owners.

    I too suffered this for a while on a Giant's Panasonic unit until I used a crazy torque force when tightening.
    .
     
  11. The Bear

    The Bear Pedelecer

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    Sounds like its something Im going to have to be checking each week then. Guy in the shop suggested it might need torquing to 42Nm
     
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  12. soundwave

    soundwave Pedelecer

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  13. The Bear

    The Bear Pedelecer

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  14. soundwave

    soundwave Pedelecer

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  15. flecc

    flecc Member

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    It is on some of these crank motor units, as you see from the two reports above of this on the Giant Panasonic units and very many cases on the Bosch units.

    Because it is just on the crank motor units and not common on ordinary bikes as you say, I suspect the makers haven't appreciated the precision necessary in the pedal shaft manufacture to ensure stable crank arm seating.
    .
     
  16. soundwave

    soundwave Pedelecer

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    maybe buy some better fitting cranks then? not had any problems with my xduro ones and my miranda carbon cranks.
     
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  17. flecc

    flecc Member

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    Maybe, but it could be the pedal shaft that's more at fault than the crank arms. The motor unit makers are making or having made their special pedalshafts, something they haven't been familiar with doing, but no doubt they buy in the crank arms from standard supplies so they should be ok.
    .
     
  18. If the bike is under warranty, the crank-bolt should be covered as there's nothing the customer can do to make it fall off and it's not a wearing or service part.
     
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  19. The Bear

    The Bear Pedelecer

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    Thats what I think as well.
     
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  20. The Bear

    The Bear Pedelecer

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    Managed to acquire a new crank bolt today. Took my bike to a different branch of the shop whom I bought it from, they didn't have one in stock so ordered one in for me.

    Rang a different branch who had one in stock, but was told it was not covered by warranty and would cost me £6. Went to pick it up and took my pedal and arm, but turned out I needed a different bolt which they didnt have, but one of the workshop lads took one off a display bike and gave it to me free. To torque this correctly I've ordered a set of allen key sockets for my 1/2" torque wrench. It's going to be something I check now on a regular basis.

    They told me its an ISIS crank bolt, but looking online I'm not so sure it is, looks more like a TruVativ bolt. Heres mine...

    [​IMG]
     
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    #20 The Bear, Mar 17, 2018
    Last edited: Mar 17, 2018
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