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I have an electric bike with internal hub gears on the rear wheel, so no derailleur. This means that for the chain to stay tight, the wheel axle needs to be dragged back into its seating before it is fastened so there is enough tension. However, ever since I removed my rear wheel once to change its tube, the wheel axle won't stay aligned. The side with the chain keeps slipping a few millimeters out until the wheel is at an angle and one side almost touches the brakes and frame, and also makes the chain loose so that it frequently pops off the sprocket.

It's driving me crazy, I've tried like five times now to readjust the wheel and fasten it, yet after riding for a kilometer it slides back. It happens no matter how much I tighten the nut.

I can see on the metal of the frame that the jagged washer of the nut has eaten into a bit and made marks, can this be the cause? What can I do about this?

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    Just a thought: Are you sure that the washer is seated correctly? The asymmetrical part of the washer needs to grab into the slit of the dropout. If that is the case, and you still have a slipping axle, well, you didn't tighten the nuts well enough. Those nuts need quite a bit of torque as the force with which the chain pulls on the axle are immense. For normal bikes, that force can easily reach twice the body weight of the rider (200kg for a 100kg rider!), more on an ebike with the motor in the bottom bracket (the force of the motor adds to the weight).
    – cmaster - reinstate monica
    Sep 24, 2018 at 20:06
  • @cmaster I think I used the word washer incorrectly, there is actually no separate washer, only the nut which has a jagged underside. The other side actually does have a washer with a tab that goes into the slit. I guess I should get one for this side too, but I am having trouble finding a place that sells them without huge shipping cost to my country.
    – GrixM
    Sep 24, 2018 at 20:27
  • Well, if your nut has a jagged underside, it seems that the washer's function is integrated into the nut. So another washer underneath the nut likely won't help, or may even be counterproductive. I think, you are back to tightening the nut more...
    – cmaster - reinstate monica
    Sep 24, 2018 at 20:51
  • Another thing to consider is a bad bearing. If a bearing in the hub is bad it can place torque on the axle and cause it to twist, loosening one side of the hub and tightening the other. If I'm correctly remembering which is my right hand, the chain side nut would be loosened in this situation.
    – Daniel R Hicks
    Sep 24, 2018 at 21:12
  • @DanielRHicks We are talking IGH with dropouts here. The IGH itself has a torque lever (this is a must for IGHs), and the axle should be flattened to fit into the dropouts. There is not much that can rotate in such a setup...
    – cmaster - reinstate monica
    Sep 24, 2018 at 21:23

1 Answer 1

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The short answer is the axle nuts need to be done up tighter than you are doing them up it now. If you can't tighten them more, you need a longer wrench to be able to apply more torque.

There are tension adjustment devices that fit over the axles and in the dropouts that make tensioning the chain and aligning the wheel easier, and help prevent the wheel moving.

According to Park Tool, the nuts should be tightened to about 25Nm; see their video on single speed (or IHG) bikes for how to estimate that torque if you don't have a torque wrench.

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  • Even though I pressed so hard that it hurt in my hand, the wrench I used was pretty small.. I guess I will try buying a bigger wrench with torque indicator. Thanks
    – GrixM
    Sep 24, 2018 at 20:36
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    @GrixM Torque wrenches are kinda expensive but are the ideal tool. For high torque uses on a bike there are cheaper ones (for general car repair use) than shown in the video. A long wrench 25-30cm should allow the bolts to be done up tight enough.
    – Argenti Apparatus
    Sep 24, 2018 at 20:55
  • @GrixM For these nuts, it's very beneficial to use a wrench with a ring that grabs the nut from all sides. Contrary to the mouth shaped wrenches, these wrenches make use of all six sides of the nut, are themselves mechanically more stable, and are very resistant to slipping off the nut while tightening it. This gives you much less potential to damage things while allowing you to screw the nut tighter. The best wrenches have a mouth shape on one end, and a ring for the same nut size at the other.
    – cmaster - reinstate monica
    Sep 24, 2018 at 20:57
  • @GrixM cmaster refers to a box or ring wrench, and they are a good idea. A socket and long bar work well too.
    – Argenti Apparatus
    Sep 24, 2018 at 21:59
  • Some of these nuts are 15mm. A pedal wrench will do nicely in that case.
    – Carel
    Sep 25, 2018 at 6:55

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