So I picked up a mountain bike from a local auction for $50. It was missing a seat and the rear derailer was bent and broken off. At the time the threads on the hanger where the rear derailer attaches worked, though they were pretty messed up. After messing with it to much, and trying to re tap the hole it became to stripped to use.

So I have this nice new bike that's all cleaned up, new break pads, new seat etc. .. but I can't attach the rear derailer.

I can't just drill out the hole and use a bigger bolt because the the bolt on the derailer is a special shape, and part of a berring.

The best fix I've found after searching online are these coil thread repair inserts. FIX-A-THRED, Helicoil are two brands that I've found. Has anyone has any experience with these?

The only problem is this was supose to be a cheap bike and a helicoil kit is around $20. So I'm looking for other suggestions on how to fix this.

I have a tap that is the right size, but I don't have access to any sort of welder. Is there any other material that I could plug the hole up with before I drill it out and re-tap it. Polyester resin? Solder? Anyway thanks in advance.


eric

If it has horizontal dropouts you could whack the hanger off and make a single speed out of it.
Both of the repairs work, I would spend the money and get one of them done. I like the helicoil better but you need a wide dropout for it to work well.
You could braze in the hole if it is steel. If you fluxed it then heated just enough to get flow, the brass would fill the threads. You could then retap. this would probably work.

What do you mean a wide dropout? What would i need to "braze" the hole with brass?

eric

Drill out the hanger. Insert a commercially available threaded insert designed specificaly for this application (check LBS). The insert installs from behind. When the derailleur is threaded in it pulls and holds the insert in place.

option 2. Depending on the hanger style you can cut it off and use a 'bolt-on' hanger. Check your LBS for the hanger.

Man, I didn't even think of that. Miamijim has it, use the bolt on hanger, if it will fit. That would only be a couple of bucks.

Or use a drop saver from Wheels https://wheelsmfg.com/p_tools_other.html
Drill out the trashed threads and inset the threaded adapter.

Variation on the same theme: www.loosescrews.com search for part
# WB-DS2. Probably sourced from Wheelsmith. $9.50 for a nut. If you
have a tap, a lathe, and drill you could make one.... Steve