Question on replacing the rear derailleur
 

My son managed to break the derailleur of his Mongoose mountain bike without any accident. I was surprised to notice that the piece that connected the derailleur to the hanger was actually made out of plastic (obviously didn't pay attention when I assembled it).

I located the direct replacement based on the model number but I am a bit hesitant to get yet another plastic one. I understand it's designed to break without harming the frame but biking around the neighborhood didn't really stress it so wondering if another 7-speed derailleur will work. How do I identify a compatible one? I see many options within the same price range without the plastic part.

Can't post any links or photos yet. Here is the derailleur - amazon com/INKESKY-Shimano-Derailleur-RD-TZ31-Mountain/dp/B07GV14SLS/

Thanks for any suggestions.

I would duplicate the piece out of a piece of aluminum flat bar if its possible.

Get a universal claw derailleur hanger/adapter and then get any 7-9 speed derailleur. An older Deore/LX, or similar, (eBay) out of the 90’s and be done with it.

John

The plastic is fairly complicated, not easy to duplicate :(

Yeah, I looked at it with Google. I see what you mean.

Thanks! Will look for an inexpensive claw hanger.