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I have an old bike in which the rear axle is like you can see in the pictures below.

It has pedal-brake. I've been struggling with the wheel alignment with respect to the bike. Each time I put it in, I align it as much as I can making sure the chain is straight (the cogs are aligned) and then I press the axle nuts as much as I can trying to keep that alignment. After a bit of cycling the wheel moves a bit in such a way that the front and rear cogs are not properly aligned, making the chain to go off the cog very easily.

What am I doing wrong? How can I solve this?

left side 1 left side 2

right side 1 right side 2

EDIT: could this chain tensioners fit my bike?

chain tensioner

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    Answer to your edit is "yes".
    – Mike
    Commented Jun 21, 2018 at 12:24
  • I notice your bike has a big kickstand on the back. Does that get used? Does it put leverage on the wheel nuts? Could be lowering and raising the stand is enough to slowly work the wheel nuts looser over time.
    – Criggie ♦
    Commented Jun 21, 2018 at 12:36
  • The pictured tugnuts could help if you had some way to secure them to the bike. As pictured, they don't seem able to bolt through any holes and retain the axle. Even if they did, your loosening axle nuts would eventually fall off completely, which is bad.
    – Criggie ♦
    Commented Jun 21, 2018 at 12:38
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    +1 for a clear description of the problem, plus photos with enough detail that people can see how things are connected.
    – shoover
    Commented Jun 21, 2018 at 16:55
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    @criggie about the stand: I don't think so, because I almost don't use it but mainly because this happens after one single use (if I go fast enough)
    – myradio
    Commented Jun 23, 2018 at 9:12

4 Answers 4

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  1. Is the chain too long? It looks like you have to move the rear wheel to the back-most position. For a new chain, you want to be around 1/3 away from the front-most position.

  2. Single-speed bikes have the problem that the axle is pulled forward by the force of the chain. Most single speed bikes use a chain tensioner if they don't provide another mechanism that pushes the hub back. You can try to retro-fit a chain tensioner.

  3. Your hub has an arm that keeps it from rotating but which can also help to protect it against moving forward. Make sure it properly fixed to the frame.

enter image description here

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    the dropouts of the OP's frame are not suitable for chain tensioners you proposed. Also the coaster brake arm, that attaches onto the frame, is placed on the other side of the frame, thus it is not keeping the problematic side of an axle in place.
    – Mike
    Commented Jun 21, 2018 at 10:14
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    1. I can check, in the picture (sorry I didn't mention it) the chain if off the cog. 3. As @Mike said, being on the other side maybe it doesn't help that much, but I certainly try to fix that a lot as well. 2. I was looking at those things and that might be definitive solution but those that you showed are indeed not suitable. I'm editing the question and posting a picture of other kind of chain tensioners, do you thing this might fit my bike?
    – myradio
    Commented Jun 21, 2018 at 12:16
  • @myradio If the wheel is moving in the dropouts, then chain tensioner will not help you.
    – Criggie ♦
    Commented Jun 21, 2018 at 12:19
  • Random factoid: in Europe most singlespeed or hub gear bikes have forward facing dropouts, serrated washers and no chain tensioners. In general they work just fine.
    – ojs
    Commented Jun 21, 2018 at 21:04
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I suspect you either are missing the lock washer (toothed lock washer, picture follows) on the drive side or the one that is there is worn out. Place one outside of the dropout, between the dropout and the hanger for the rack/stand.

And the promised picture of the washer I meant:
lock washer

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  • Indeed this might be the problem (or the solution). I don't recall if there are these in the bike. In any case I can add them/update them. Could it be that instead of these I have a striated nut?
    – myradio
    Commented Jun 21, 2018 at 12:22
  • @myradio, I think you mean "serrated" and yes, you should have those. Nevertheless, look at the non-drive side of your bike. What you have there (inside out) is: wheel bearing cone -> lock washer -> rack/stand hanger -> washer -> nut. On the drive side it's the same only it is missing the lock washer. Since the dropout can shift relative to the rack/stand hanger, if not fixed properly (sufficient torque or some other solutions like lock washer or adhesive) the wheel comes out of alignment.
    – Mike
    Commented Jun 21, 2018 at 12:30
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The underlying problem here is that the wheel's axle is moving in the dropouts.

I think your wheel nuts are not biting down enough to properly resist the tiny flexes of the bike while riding. When the nut has undone a little, its looser in the dropout and the pressure of your foot is pulling the right-side of the hub forward.

Assuming you're using appropriate levels of torque on the wheel nuts, they should not move at all.

I've had this on a cheap QR, where the ridging on the axle nut was worn smooth. I had spare time and no money so I spent time filing the grooves deeper and sharper using a rats tail file.

https://i.ebayimg.com/images/g/Zf0AAOSwajVUUOPC/s-l300.jpg

The second part of this is if your rear dropouts are not parallel. Even a single degree is enough to stop the nut and axle from pressing flat against the dropout. This allows flex with each pedal stroke. and the nut backs off, again allowing the hub to move under pressure.

I had this exact problem on my cold-set MTB frame when changing from 5 speed to 9 speed hub.

From https://www.sheldonbrown.com/forkend-alignment.html

See https://www.sheldonbrown.com/forkend-alignment.html for more info.

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The simple answer is that the axle bolts need to be torqued up tighter, so they grip the frame better.

Use a proper box wrench, not an adjustable wrench. A short length of metal tube slipped over the wrench will give you more leverage.

Alternatively, take the bike to a local bike store and have them torque the bolts. Be prepared for them to point out all the things wrong with the bike that they want to fix.

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  • According to bicycletutor.com/torque-specifications the torque for wheel axle nut is between 30 and 40 Nm - it is roughly the weight of 3 to 4 kg of a 1 meter lever on the wrench. Or 12 to 16 kg on 25cm lever. It's not that much and tightening it more will put unnecessary strain on the axle.
    – Mike
    Commented Jun 21, 2018 at 10:45
  • To clarify, I'm not suggesting using a 1 meter tube for leverage! Maybe just doubling the length of the wrench.
    – Argenti Apparatus
    Commented Jun 21, 2018 at 10:48
  • @ArgentiApparatus, 30 Newton-meters isn't much torque. Even on a stubby 15-cm wrench, it's only a 20-kg weight. (To put it in context, that's roughly equivalent to asking your five-year-old kid to pull as hard as possible on the wrench.)
    – Mark
    Commented Jun 21, 2018 at 21:58

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