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
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)