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I had a slight bend with my mech hanger so I took off the rear mech to get the hanger out and fixed.

Now that the hanger is fixed, I noticed a U-shaped ring around the bottom of the bolt on the rear mech is preventing me from fully tightening the mech to the hanger.

There is a opening on the top that seems to fit around the hanger but because of the ring, the mech is not fully engaged and the opening's edge ends up scratching the hanger.

Any ideas?

Thank you

enter image description here

Update:

Not the best angle but this is what it looks like when screwed in furthest. Ring is still in groove and B-screw is on tab.

From here if I were to increase B-screw angle, that open would move over and scratch the hanger, which didn't seem right to me but I couldn't find anything about this from Shimano manuals.

Just tried to align both open ends, still a gap there.

enter image description here

More info: Not the best angle but this is what it looks like when screwed in furthest.

@Argenti, yes ring is still in groove and b-screw is on tab.

From here if I were to increase b screw angle, that open would move over and scratch the hanger, which didn't seem right to me but I couldn't find anything about this from Shimano manuals.

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  • Rotate the C ring clockwise about 45 degrees.
    – Daniel R Hicks
    Jul 12, 2019 at 18:43
  • That C shaped bit goes by names like "shaft retainer clip".
    – Kaz
    Jul 12, 2019 at 23:44
  • Could we have a picture from the same POV as the one in @Kaz 's answer?
    – Carel
    Jul 13, 2019 at 16:17

2 Answers 2

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That black strip to which your derailleur is attached, which can be assumed to be the hanger, looks strangely narrow, like a metallic popsicle stick. Is that by chance a part related to the Shimano Direct Mount (TM) system? Some sort of adapter link plate? It seems incompatibly narrow for the derailleur: it's fitting entirely into the semi-circular gap in the derailleur's bolt plate (what we're calling "the opening" in this Q&A.) That shouldn't be happening; the hanger shouldn't be pressing against the axle retainer clip at all.

Assuming there is no other compatibility issue, and you want to keep that hanger, one way to fix this would be to put a suitably dimensioned stainless steel washer between it and the derailleur, to effectively make the hanger look as if it has a larger area around its receptacle for the derailleur to mate with.

The real fix is to install a traditional standard mount hanger that is compatible with the Sora.

For reference, here is a picture of how my Sora is attached to a standard type hanger. Notice also how the hanger is angled; it doesn't protrude rearward, but slants forward, so it doesn't anywhere near align with that opening recess in the derailleur's end plate.

Shimano Sora Rear Derailleur on standard hanger

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  • Yep, that hanger does look strange.
    – Argenti Apparatus
    Jul 13, 2019 at 0:56
  • Honestly? Your hanger looks like its been bent twice to work around some alignment setup. Is your bike modified? I can't recall seeing a bent-by-design hanger, but there are some that have different levels that were milled or cast.
    – Criggie ♦
    Jul 13, 2019 at 1:52
  • @Criggie I think I understand what you're seeing; there is a a perspective trompe l'oeil happening in the photo. The hanger is a actually flat, but its "question mark" inflected shape makes it look like it's jutting out to the right. The base of the wheel skewer nut, and of the derailleur swivel plate are both actually in the same plane! If you stare at it for a while, your brain will see it both ways.
    – Kaz
    Jul 13, 2019 at 3:27
  • @Kaz Oh I see - yeah that's an interesting illusion. I could see a clean bit that looked like the top of the "bend-out" piece.
    – Criggie ♦
    Jul 13, 2019 at 3:36
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    @Erwann Yes, that's the point. That gap in the bolt plate isn't supposed to mesh with anything.
    – Kaz
    Jan 15 at 18:17
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That ring is to keep the bolt captured on the derailleur body. Check to see if it is seated properly. It should lie in a groove, and not have ridden up on the thread at all.

Make sure the B-screw tab (at 9 o-clock relative to the derailleur bolt in your photo) is located on the hanger properly. The derailleur body rotates under spring tension around the B-pivot so you need to wind the tab back against the spring to position it properly.

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