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I got a low-quality walmart bike for free in decent condition. I am trying to make it rideable. I have given up on the stock derailleur and bought a cheap shimano tourney direct mount derailleur to replace it with. I did not realize, however, that the old derailleur was a hanger mount derailleur. That means I need an appropriate bracket to mount the new derailleur. What bracket do I need?

(I am trying to avoid buying another hanger mount derailleur because the only one I am seeing is the RD-TZ31, which came stock on the bike and gave me nothing but trouble.)

Old derailleur:

Image

New derailleur:

Image

The attachment point on the bike:

Image

The old derailleur hooked around the axle bolt, and the extra little bolt also went into the dropout. I have no idea what the purpose is for the two holes above the dropout.

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You need a ~$5 claw hanger.

Do not try and salvage the one off your old derailleur - they're generally pressed together and don't have enough metal to tap for a hole. Guess how I know that.

The only problem comes with the positioning - you may have to bodge things a little and compromise to find what works best.

enter image description here

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    I saw these on amazon, but I also saw this webpage which suggested that I specifically need a "direct mount" hanger, and these look to me like the "conventional mount" hangers, though I don't know for sure.
    – Edward
    Sep 27, 2023 at 3:17
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    @Edward it's correct for the derailleur in your photo. Shimano also make the Tourney in the style that matches your bike if you can take it back for an exchange.
    – Noise
    Sep 27, 2023 at 7:36
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    I ended up buying one of these and installing the derailleur. It's clearly meant to be installed at a specific angle, at any other angle it will likely shift unless you really tighten it with gorilla strength. It put the top pulley right into the cassette and I couldn't shift below the highest gear. I tried bottoming out the B-screw on the derailleur and it made no difference..
    – Edward
    Sep 29, 2023 at 2:22
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This is a "direct mount" derailleur, so you will need either:

  1. A "direct mount" derailleur hanger, or
  2. A "conventional mount" hanger with an appropriate adapter or "b-link" so that the derailleur attaches at the correct location.

You can read about the two different standards here. In summary, direct mount derailleurs need to attach further back than conventional mount derailleurs.

Unfortunately, I could not find a suitable direct mount hanger or "b-link" for sale. Using the conventional mount hanger with a direct mount derailleur without the adapter link is unlikely to work at all- it certainly did not for me. This left me with no way to use this derailleur, so I had to exchange it. If you need to replace a derailleur on a bike like this, your viable options are:

  1. Get a "hanger mount" derailleur, like the old one pictured in the question- selection is very limited but there is one in the tourney series (thanks @Noise). This is what I did.

  2. Get a "conventional mount" derailleur and use the conventional mount hanger, like the one @Criggie mentioned (also pictured below)

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