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I have an 8 speed where I couldn't index the shifting properly without it skipping a gear. 8 - 7 - 6 then it skips to 4. (There's also another skip in gear 2-3). If you adjust it to shift to gear 5, you then make it unable to shift to gear 7.

This all started when I bumped my RD on a rock, at first I thought it was my shifter that's broken, but I recently changed shifters and the problem is still there (I even had all the cables and housing replaced).

Im starting to think it's the RD that's broken, but there's nothing noticeably wrong with it. It's not bent or anything.

Banjo Panesa
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    Have you checked if the RD respectively the mech hanger did take any damage? I wouldn't put that out of the equation if I knew it hit a rock recently. Not 100 percent sure if that is the case by your description but being unable to get all shifts right is often caused by that, I also had that on my road bike once or twice. – DoNuT Jan 06 '24 at 13:17
  • @DoNuT yes. I checked the alignment. Although I'll have a mechanic check on it tomorrow. – Banjo Panesa Jan 06 '24 at 13:22
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    @DoNuT that is an answer, and it is likely correct. 11 and 12s systems are very sensitive to hangar misalignment, even that which you can't see visuallty. – Weiwen Ng Jan 06 '24 at 16:29

1 Answers1

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Based on experience and the fact that the RD had an impact, the most likely cause is still a bent derailleur hanger, even though no misalignment is visible. The hanger is designed to be the weak part, so a bend after a crash, fall or impact is likely and expected. Better swap a cheap metal/aluminum part than your derailleur or damage an expensive frame.

Not getting consistent shifts all across the cassette (even if the majority of gears works fine) is a very common symptom of misalignment due to a bent hanger, I had that more than once on my road bike. Even though I couldn't identify any damage/bend visually, I never got to a fully acceptable result by adjusting cable tension. The local bike shop confirmed misalignment when I took my bike to repair and afterwards, tension adjustment is a one-minute job as it should be.

You can try straightening it as described here, swap the hanger or take it to a shop for them to do the job for you.

8-speed with wider cog spacing probably isn't as sensitive to damage as modern 11/12-speed bikes but there is always a "too much".

DoNuT
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