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enter image description hereI bought a bike on Ebay which has a Sora groupset. The rear derailleur is noisy and jumps in and out of gears despite much tweaking. I've given up on it.

What derailleur can I buy that will work as a drop-in replace of the Sora derailleur without my having to also change the cassette or shifters?

The Sora is either medium or long cage - not sure which. It has approx 3.25 inches between jockey wheel centers.

Cassette has 32 teeth on largest ring.

EDIT: Just found someone else with the same problem. Mine sounds much the same as this: Noisy rear derailleur (Shimano RD-5800)

EDIT2: Motivated by your comments and after a bit of a clean and a bit more of a systematic re-indexing as per the video linked in the accepted answer (which I just changed below) the derailleur noise is in fact much improved. It's still not perfect but it's good enough.

TY!

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  • That's not inherent to 9 speed sora - I've got the same. I assume it's clean, but has it done a lot of distance? How old are the cables?
    – Chris H
    Commented Apr 1, 2019 at 20:43
  • I've read positive reviews on the Sora - is it possible the derailleur or the derailleur hanger is bent?
    – David D
    Commented Apr 1, 2019 at 20:44
  • Photo added. Excuse excessive lubrication which has helped some.
    – Claud
    Commented Apr 1, 2019 at 20:58
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    Have you measured the chain wear? Is the cassette worn much?
    – Swifty
    Commented Apr 2, 2019 at 8:08

2 Answers 2

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As a sort of addendum to Nathan Knutson's answer, focusing on things to do before replacing the derailleur.

  1. Make sure wheel is fully in the dropouts and parallel to the frame.

  2. Properly and clean the drivetrain with a degreaser and apply a bike chain specific lubricant, not penetrating oil such as WD-40, GT85 etc. There are many videos that show how to do this.

  3. Check hanger alignment. From the photo it looks pretty good (cage should be parallel to the chainrings). It might be worth getting a bike store to check it with a hanger realignment tool.

  4. Replace cables and housings. Stretchy cables and sticky housings can cause the derailleur to not index properly.

  5. Run through a systematic derailleur adjustment process.

  6. Check chain and cassette wear.

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    +1 for checking chain wear. Also on a used bike don't assume that the chain is the correct type.
    – mikes
    Commented Apr 1, 2019 at 23:27
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    Also, specifically check the rear shifter cable for fraying at the right shifter housing itself. Shimano shifters tend to have the shift cable make a bend right where it enters the shifter housing, and that bend is prone to fraying. Just one or two frayed strands of cable can really mess up rear shifting. (And of course, the opposite is true too: the cable can fray very badly with no affect on shifting until it snaps entirely....)
    – Andrew Henle
    Commented Apr 2, 2019 at 9:35
  • I've edited my original post with EDIT2... just a superficial clean and a re-indexing sorted it 90% better. TY.
    – Claud
    Commented Apr 2, 2019 at 12:59
  • Halfords looked at my v old mountain bike. The chain is 3 years old, with infrequent use but was already stretched to end of life. The nice man said that's what happens when you don't change the cassette when you change the chain. Never occurred to me.
    – Emma Atkinson
    Commented Apr 27, 2023 at 8:14
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For 9-speed (or 10-speed, which uses the same actuation and usually works fine in this instance) with native 32t clearance, the options for a Shimano road group model are pretty limited due to how the chronology played out with 32t road cassette being a thing. A lot of the 11-speed road GS cage derailers can clear 32, but they won't work with your shifter. The one you have and Claris RD-2400-GS may be the only nominally road ones that would work as a drop in replacement. RD-2400 is okay, barely.

Another answer is to get any GS or SGS (much more common) mountain 9-speed derailleur, which are compatible because Shimano 9-speed mountain and road rear derailleurs use the same actuation ratio, and all the 9-speed mountain RDs clear a 32. Of these there are a lot of choices; some currently produced ones are RD-M590, RD-M591, RD-M4000, and RD-M772. The XT RD-M772 may be the only one currently produced that comes in mid-cage/GS like you presumably need. That would be a good choice for a bike that's going to get used a lot.

Of note is that it's exceedingly common for rear derailleur hanger alignment as well as cable issues to cause the problems you're talking about, and you really shouldn't go to replacing the derailleur until those are eliminated as possibilities, unless you can tell the RD itself is obviously bent or slopped out, which does happen. And if the RD itself is bent, usually the hanger will be too from whatever incident(s) caused it, which will need addressing for a new RD to work correctly.

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  • Thank you! I have now added a photo of the offending item. It's clagged with GT85 which has helped a little. Can you tell if it's bent or otherwise badly configured?
    – Claud
    Commented Apr 1, 2019 at 20:57
  • If it is bent, it's not by much. It's hard to tell from a picture. Cable friction or other issues are common too. Another test is to grab the RD and test for slop in the various pivots, which can cause poor shifting.
    – Nathan Knutson
    Commented Apr 1, 2019 at 21:03
  • My experience with 9-speed MTB derailleurs on Shimano 10-speed road shifters is they work ok, but not all that great. I've done it on two bikes, one with Ultegra 6700 shifters and one with 105 5600 shifters. Neither shifted all that well - there were always a few gears that needed extra coaxing to shift into, and one or two where the chain would clearly indicate it wanted to be somewhere else on the cassette. Usable if you need the 32, but definitely not DuraAce RD-7800 shift quality. The RD-7800 is still, IMO, the best-shifting rear derailleur I've ever used.
    – Andrew Henle
    Commented Apr 2, 2019 at 9:43
  • @AndrewHenle The OP has a nine speed shifter. FWIW I think you're right that 9-speed RDs on 10-speed road drivetrains can be a little hit or miss. I think it tends to work fine with XT and XTR RDs in good condition.
    – Nathan Knutson
    Commented Apr 2, 2019 at 17:48

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