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I've got a very old used bike. It has a bunch of issues I'm trying to fix at once: the derailleur is not keeping the chain tight only in certain gears, the back wheel wobbles slightly and over time gets pulled forward to the point of rubbing against the frame.

I took the wheel out and determined that there is probably some minor wobbling coming from something being off with the bearings but I decided not to take it apart, just live with it and try to put the wheel back pulled further back and somehow fixing the derailleur/gears issue too.

I figured out that there is one specific configuration when everything seems to work, see it on the photo below. (Note, the axle needs to be completely pulled back on the side pictured, but on the other side slightly more forward than that, that's the only way to have the wheel aligned with the line of travel at the middle of the frame). In this angle, the derailleur is able to keep the chain tight for all gears.

The issue is that now if I start pedaling or shifting gears, eventually the derailleur is forced to rotate counter clockwise and the axle is pulled forward so that I'm back at my original issues. I just can't seem to figure out how to maintain this specific position

How could I solve this?

Edit: I'm adding below a second image from a different angle

Update:

Thank you for all the comments and suggestions! Based on them, I plan to do the following:

  • Fix wobbling of the wheel by replacing bearings so that I'll be able to move the wheel forward
  • Replace the derailleur hanger and the mounting bolt attaching the derailleur to it
  • Use axle nuts instead of the regular ones and remove washers from the axle
  • Replace cable housing and possibly the chain too

To do the above, I'm having two new challenges:

  • How to unscrew the super tight and somewhat rusty current attachment of the derailleur to the current hanger? (see picture below)
  • Where can I find a suitable replacement mounting bolt that would allow me to attach the derailleur to the hanger so that it can pivot? (see part #2 and connecting parts in David D's answer)

Image of the working but unstable position

Image from other angle

Image of the stuck and rusty attachment

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  • What's that brownish dish thing that is about where the smallest cog would be? Some kind of chain guide or spoke protector-like disk, but at the other end of the cassette? – Criggie Mar 8 at 5:42
  • Looks tot me like your derailleur hanger is severely misaligned (derailleur incorrectly mounted. The small hole in the derailleur hanger next to the slot where the wheel's axle is currently located should be aligned with dropout slot – Maarten -Monica for president Mar 8 at 9:16
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That's one seriously chopped-around bike. I see a bolt holding the rear derailleur on, on an axis that would normally pivot. This means your B tension is non-existent or infinite depending on the gear chose.

I also see the hanger well out of position and missing its other bolt. That means the derailleur is at a funny angle. Attempted `shopping below:

Additionally, what's that brownish dish thing that is about where the smallest cog would be? Maybe its supposed to be there to stop the chain dropping off the littlest cog ??

I suspect your chain will also be too long, once this angle is all corrected.

The gear cable outer also looks kind-of lumpy, as though the metal reinforcement is kinked or broken. This may cause issues, or with friction shifters it may simply provide vagueness while shifting.


The wheel is sliding forward in the dropouts because its either not tight enough, or there's not enough resistance. I think the axle nuts look like generic hardware store nuts, and will probably lack any serrations underneath. Some time with a file could restore rounded serrations back to grippier ones, but really some new axle nuts would be better.

Your image
This is your image, simply rotated so its about normal angle. From this you can see how far back the derailleur is.

Here are some lines drawn on top of your image to show the angle difference: enter image description here
That empty little hole in the hanger is missing a special bolt, which stops it rotating around the axle and undoing your axle nut and holds the derailleur on when the wheel is out.

This is a conventional claw hanger - there is nothing special here, these pre-date all the unique weird custom hangers. These are worth around $5-10 of most currencies - it would be easier to buy a new claw hanger than mess around trying to make that weird nut on the back.

enter image description here

enter image description here
This mess is a mochup of where your derailler should be sitting, relative to the axle. This position means there will be more teeth engaged at once with the chain.


Another realisation just now - you have a stiff link in your chain.

enter image description here

This results in a noticeable click or clunky every 4~5 crank revolutions, as this inflexible link passes through the derailleur's jockey wheels. This is probably the point that the chain was closed up at fitting time, though it can be caused by dirt.

To fix it, grab the chain in your fists on either side and try to bend the chain sideways. Start with enough force to open a loose jar-lid, and work up to a bit more if the chain doesn't come free in that link.


And finally - you say that the loose bearings are something to live with now. I suspect this wobble is also contributing to the sloppy gears, because as the wheel moves it will move the whole cassette too. I would totally recommend tuning up the bearings, and perhaps a clean and re-grease if you possibly can.


In summary - I think this is fixable. It will never be perfect, but I'm sure it can be better.

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    Yes, the brownish dish is for stopping the chain dropping in that direction. And yes. the shifter is kind of vague and the chain is probably too long because of being worn.. – reka Mar 8 at 6:20
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    One of my first tasks when cleaning up an old bike that someone wants to ride is repacking the hub bearings and ridding it of annoying and dangerous wheel wobble. When that's complete the chain has had plenty enough time for the wd-40 to work it's magic so it's prepared for cleaning and proper lubrication. Amazing results and now a decent platform from which to deal with derailleurs and brakes. – Jeff Mar 8 at 22:27
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    @Criggie, thank you for all the detailed explanations and photos!! Regarding the claw hanger and that hole in the frame being for other things, does that mean that my bike currently does not have a place for the little hole of the hanger to attach to and that is why I need the special kind of hanger? And for the wheel sliding forward, when I replace the axle nut with one with more resistance, should I still keep a washer underneath? (Currently the regular nut has a washer right below which is not visible on the photo) – reka Mar 9 at 16:56
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    In addition, @reka, I'd suspect that the dropouts (where the wheel slides into) are not parallel. This would allow one side of the wheel to slide forward and no longer be neatly lined up between the brake pads. With a bike this age, it's easy for one of them to have been bent during some abuse by a previous owner - simply dropping it on the ground or having been stored for some time with weight on the side of the frame could have caused this. – FreeMan Mar 9 at 20:04
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    @Maarten-Monicaforpresident, I've just added that photo. Yes, it seems based on the other answers, that I'll have to move the wheel forward to be able to mount the derailleur properly. And to do that, will follow Jeff's suggestion – reka Mar 9 at 22:21
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Criggie has done an excellent job of taking the original post pictures and modifying them to show how the derailleur should be aligned.

Looking at the derailleur exploded diagram at the bottom of this answer - part number 2, mounting bolt - and then looking at the picture in the original post the mounting bolt has been replaced with what looks like a sawed off wheel axle and nut.
enter image description here

The derailleur should be able to pivot on the mounting bolt. If the axle/nut combo does not allow movement that will contribute to the other issues

It helps to see pictures of how things are supposed to be.

Hanger attaching to dropout. (page 12). enter image description here

Correctly installed derailleur
Notice the smooth curve of the derailleur cable housing.
enter image description here

Here is an exploded diagram of the SunTour VX derailleur
enter image description here

enter image description here

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  • Thank you for the clarification and photos!! This all is very helpful! I didn't realize before that the derailleur should be able to pivot, I'll definitely have to fix that. I was trying to find an equivalent piece online (for item#2, the pivot mounting bolt) without much success so far, do you happen to know where I could get one of these? – reka Mar 9 at 23:15
  • Added a line to the green frame photo showing where the slot is relative to the hanger's bolts. Feel free to remove or include if that helps. – Criggie Mar 10 at 3:19

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