Forum home› Road cycling forum› Workshop

Sora rear derailleur- replacement compatabilty?

tonysjtonysj Posts: 391
in Workshop
Hi all.
My winter bike Btwin Triban 520 with shimano 9 speed Sora and I've had issues with indexing the rear derailleur.
Ive had to change to a 105 RD, older model, as the derailleur to hanger had a crazy amount of play causing the indexing to be out no matter how much i tweek it.
Ive since replaced the inner and outer gear cables but it still wont index cleanly.
Have i got a compatable RD for the Sora 9 speed with a 105 RD?. Not sure if its 10 or 11 speed but looks like markings are RD5800.
Thanks for any advice.
Tony.

Posts

  • whyamiherewhyamihere Posts: 7,678
    A 5800 derailleur won't be compatible with 9 speed Sora, it's 11 speed and Shimano changed the pull ratio for 11 speed road. You can use a 9 or 10 speed road derailleur or a 9 speed mountain bike derailleur, they all used the same pull ratio. The only exception is Tiagra 4700 10 speed, which also uses a different pull ratio.
  • tonysjtonysj Posts: 391
    whyamihere said:

    A 5800 derailleur won't be compatible with 9 speed Sora, it's 11 speed and Shimano changed the pull ratio for 11 speed road. You can use a 9 or 10 speed road derailleur or a 9 speed mountain bike derailleur, they all used the same pull ratio. The only exception is Tiagra 4700 10 speed, which also uses a different pull ratio.

    That explains a lot lol.
    So i can use a 9 or 10 speed RD. Ill have to find a Sora 9 speed GS if possible, straight replacement. I was thinking it was the shifter that may be worn.
    Thanks for the info.
    T.
  • PMarkPMark Posts: 159
    This is what you want:
    https://www.chainreactioncycles.com/shimano-sora-r3000-9sp-rear-derailleur/rp-prod150050?mx01=a&mx02=a

    Because bike components are in short supply at the moment, you shouldn't lose too much on your 105 if you sell it.
  • tonysjtonysj Posts: 391
    markdurdle said:

    This is what you want:
    https://www.chainreactioncycles.com/shimano-sora-r3000-9sp-rear-derailleur/rp-prod150050?mx01=a&mx02=a

    Because bike components are in short supply at the moment, you shouldn't lose too much on your 105 if you sell it.

    Yeap, that the one. Thanks.
    T.
  • stevenmewstevenmew Posts: 14
    Hey Tony, I was just wondering what indexing problems you were having. I had to replace the right shifter on my Triban 520 recently and haven't been able to get the indexing right since. Never had a problem with it until now and I'm wondering if the new cable and shifter are accentuating the play in the RD. At 20 quid the easiest solution would be to just buy a new one but I would like to know where the problem is coming from! Thanks mate
  • tonysjtonysj Posts: 391
    stevenmew said:

    Hey Tony, I was just wondering what indexing problems you were having. I had to replace the right shifter on my Triban 520 recently and haven't been able to get the indexing right since. Never had a problem with it until now and I'm wondering if the new cable and shifter are accentuating the play in the RD. At 20 quid the easiest solution would be to just buy a new one but I would like to know where the problem is coming from! Thanks mate

    Hi stevemew, since trying the 105 RD it just wont index properly and i think its the rear shift ratio of the 105 which i believe is 1.4 where the Sora RD is 1.7. I believe its this although i cant find its compatability on the net only snippets of info. The indexing just wont centre on all cogs on the cassette. Its fine with the first 3 but then runs out not being able to shift a gear per shifter change. Ive tried everything so its either the compatability, or lack of, with the 105 or at a push a f**ked right shifter. Hope its just the RD issue.
    Im going to get a new Sora RD and hope that sorts it.
    Why did you change the shifter? Was it worn out or damaged/crashed?
    Regards.
    T.
  • tonysjtonysj Posts: 391
    Stevehew, mate I read when fitying a new gear cable you should stretch it when first fitted, presumably to "bed" it in slightly. I had a lot of movement in the bolt that attaches the RD to the hanger. You could move the lower cage in and out towards the spokes and i rhink it was this "slack" when shifting up and down that was leaving the RD slightly out of place either up or down the gears. Hope that makes sense 🙃
  • stevenmewstevenmew Posts: 14
    Yeah I have exactly the same issue with the rear gears, works fine for the smallest 4 but further up the cassette I start running into issues. Having only replaced the shifter, I can only assume it's that causing the problems - like you say, incorrect ratio or something. All 9-speed shimano stuff should be compatible though, so I don't quite get it.

    I wouldn't have thought stretching the cables would cause this amount of descrepancy from the start, more like I'd have to readjust after only a couple of weeks, right?

    My shifter just stopped working to be honest. It stopped clicking at all, leaving me stranded on 3 gears getting home, then didn't respond to the WD40 bath I gave it. Curiosity got the better of me and I opened it up, at which part I saw that a part had broken completely. It wasn't particularly surprising as I've put a lot of miles into it and have slid down the road on that side too! Nothing lasts forever. Also the new shifters have under bar tape cable routing which is nice.
Sign In or Register to comment.