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I recently got a pair of Shimano 105 shifters and a rear derailleur and put them on my bike. The front derailleur is a Shimano Tiagra, and the cassette is also Shimano. The cables are new, but the outer cables are old.

I managed to get the rear mech indexed correctly when I installed them, but the following day the bike wasn't shifting to the biggest sprocket. I tried to adjust the indexing, but if I loosen the barrel adjuster enough to shift to the biggest sprocket, the derailleur won't shift to the smallest one. Similarly, I tighten the adjuster until it shifts to the smallest sprocket, it won't shift to the biggest one.

If I pull on the cable and turn the cranks with my other hand, the derailleur shifts to the biggest sprocket but the chain drops back to the second biggest when I let go of the cable.

I have looked at the invoice and the packaging, and it says there the components are supposed to be 2x11, and I counted ten clicks from the shifter. What could be the cause of this issue?

Here are a few photos of the rear mech:

Rear view:

Rear view

Now that I look at it, the derailleur cage seems to be in an odd angle. Here's the side view:

Side view

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    That derailleur definitely looks bent to me: the cage should be vertical but it's not. Also, check the exact model number of your gear: 105 used to be 10-speed so it's possible you were given an old model by mistake. I guess this is unlikely, since it seemed to work at first.
    – David Richerby
    Jun 30, 2019 at 10:32
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    @DavidRicherby that's definitely an RD-5800, RD-5700 looks different.
    – Klaster_1 Нет войне
    Jun 30, 2019 at 11:02
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    Why is the low limit screw so far in?
    – Daniel R Hicks
    Jun 30, 2019 at 12:25
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    But you said it's not shifting to the lowest gear.
    – Daniel R Hicks
    Jun 30, 2019 at 12:43
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    You should unscrew those H/L range limit trim screws and then adjust the derailleur. Then use the H/L screws to prevent the chain from coming off. It's possible for too stringent trims with the H/L screws to cause a problem like this.
    – Kaz
    Jul 3, 2019 at 23:26

2 Answers 2

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It's evident from your first picture that there is definitely a pretty bad derailleur cage alignment issue.

The derailleur hanger does not appear bent, but it does look like the derailleur bolt may be cross threaded , as the derailleur body seems to be at an angle to the hanger.

Check the derailleur installation and also check that the cage is not bent.

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    It may be simply that the bolt is not tightened all the way.
    – Daniel R Hicks
    Jun 30, 2019 at 12:45
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    @DanielRHicks Indeed. That seems more likely than cross threading, and would explain why the problem did not manifest at first.
    – Argenti Apparatus
    Jun 30, 2019 at 12:48
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    @DanielRHicks The issue persisted after I'd already tightened the bolt as far as it would go. I think the issue was cross-threading. I must have damaged the threads somehow since getting the bolt to the true threads was way harder than cross-threading.
    – HAEM
    Jun 30, 2019 at 15:24
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    @HAEM the thread in your hanger may be destroyed by cross threading a steel bolt into it, but you can of course replace it.
    – Argenti Apparatus
    Jun 30, 2019 at 15:41
  • Check the B-screw. It looks as if it's pressed against the side of the hanger. It may have been bent as well.
    – Carel
    Jul 1, 2019 at 10:06
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This Is Not An Answer - But it may help others diagnose the issue.

I'm happy for the OP to use this picture in his own question, in which case I can remove this as being an answer.

I've taken the OPs image and added straight lines to show how far out of alignment everything is, providing the image was captured along a straight plain.

enter image description here

Although the rear cage is obviously twisting outward with the lines imposed over the image you can actually see the rear cage is in line with the chain at the front derailleur.

The two larger / lowest sprockets are actually sitting way behind the front derailleur.

I cant actually see how this will work in this current state without some major cross chaining.

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  • Thank you for this. I think that the mis-alignment may be a trick of the camera angle. I know that the chain fits through the front derailleur now that I got the RD to go through the full range of motion. It might also be that my front mech needs oiling or something.
    – HAEM
    Jul 1, 2019 at 16:28

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