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New cassette: 11-32 to 11-25……Di2 now not shifting correctly. Any ideas?

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  • July 22, 2018 at 5:52 pm #28753
    rambino

    My bike’s stock componentry was Ultegra Di2 6800 (compact 11-32 / 50-34)

    Last month installed new semi-compact R8000. Chain left as was. Smooth shifting as per usual.  Very happy. All good.

    Two days ago, I ditch the Ultegra cassette/chain and add a shiny new Dura Ace C9000 11-25 cassette and a KMC X11EL (nothing out of the ordinary) – but ever since, the shifting is all out…ESPECIALLY from 11 to 10

    It actually shifts kind of OK between 9 – 1 but no where near as crisp as it was before. No amount of micro shifting does the trick. Basically, if you get it perfect in one area (near enough impossible) it goes out in another.

    For the KMC chain, I have kept the same chain length again – though it was slightly shorter due to old one having 1cm stretch – and visually it looks OK….but I can’t be 100%

    Also, mech hanger looks OK and is unlikely to have been damaged during work being carried out….but again can’t be 100%

    So, I’m confused: too long a rear mech cage… chain compatibility/length… alignment issues…bent hanger or bent cage…..or what?!

    Any ideas?

    Thanks

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Viewing 15 replies - 16 through 30 (of 31 total)
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  • July 24, 2018 at 8:54 am #923915
    0
    rambino

    Struggling to upload both of

    Can’t upload 2 at the same time for some reason, but here goes….

    Looking at the bib-big picture I’d say it almost looks like I’ve already taken out 1 too many links, right? Though, it’s not as if I’m ever going to be riding in this gear so perhaps it’s fine as is?

     

    July 24, 2018 at 6:58 am #923913
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    madcarew

    Better diagnostic photos are

    Better diagnostic photos are big-big and small – small.

    July 24, 2018 at 6:57 am #923911
    0
    madcarew
    rambino wrote:
    Thanks guys.

    Tonight I tried out my old Ultegra 11-32 – just to be sure about there being no hanger/cage damage – and the shifting was buttery smooth between all shifts.

    So, I guess that means it must be to do with the chain length and b-screw then

    I’ll have a fiddle around tomorrow and if I cant sort it out myself then it’ll have to be a LBS job.

    Oh and just one more thing… if I accidentally remove too many links on the chain, will it be OK to reinstall one of the links with the regular pin or would I need to use another quick link?

    If it is a shimano chain you will need to use a specific shimano replacement pin, but really it’s easier to just use one or more quick links.

    July 24, 2018 at 6:12 am #923909
    0
    CXR94Di2

    Before you start removing

    Before you start removing links from chains, take two side on photos of the bike showing the chain ring and derailleur in the whole photo.  One photo with the chain on the inner ring and on 11t cog and the other photo with the chain on the outer ring on the 11t cog.

    just by looking at the derailleur positon, it should be clear whether you need to remove or even get a longer chain, see my derailleur in big chain ring and 11 cog

     

    July 23, 2018 at 11:43 pm #923907
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    rambino

    Thanks guys.

    Thanks guys.

    Tonight I tried out my old Ultegra 11-32 – just to be sure about there being no hanger/cage damage – and the shifting was buttery smooth between all shifts.

    So, I guess that means it must be to do with the chain length and b-screw then

    I’ll have a fiddle around tomorrow and if I cant sort it out myself then it’ll have to be a LBS job.

    Oh and just one more thing… if I accidentally remove too many links on the chain, will it be OK to reinstall one of the links with the regular pin or would I need to use another quick link?

    July 23, 2018 at 7:39 pm #923905
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    Anonymous
    shmooster wrote:
    kevvjj wrote:
    Surely if it shifts perfectly well on a 11-32 it should have no issue shifting to a 25 tooth cog? Surely somewhere on the 11-32 cassette there exists a 24/26/26 tooth cog?

    By that logic you could have a 32-11 instead of an 11-32

    If the GS derailleur shifts from 11 -12 then 25 can’t be too small can it. Have a think about it…

    July 23, 2018 at 6:51 pm #923903
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    madcarew

    Your mech is no issue as it

    Your mech is no issue as it is designed to shift on any sprocket down to a 10. The shimano recommendation is that if going above a 28 for largest sprocket you will need a gs derailleur. The issue is simply chain length. You have about 6 extra links in it. Fix this and the B screw and you will be fine.

    July 23, 2018 at 4:55 pm #923901
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    Jimthebikeguy.com

    As above, your chain is too
    As above, your chain is too long,so is your mech,and your b screw is way out. Fix all 3.

    July 23, 2018 at 3:00 pm #923899
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    VeloUSA

    Two issues you are faced with

    Two issues you are faced with.

    1. If you’re running a GS cage, Shimano states low sprocket minimum is 28t. Yeah, didling aound with the b-screw might get it to work but the spring tension will be off causing the 10-11 shift issues to occur. Ideally an SS cage for 11-25 is the better match.

    2. Shorten your chain. Here’s an how to video..skip to 3:34 for mathmatical formula.

    July 23, 2018 at 2:55 pm #923897
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    shmooster
    kevvjj wrote:
    Surely if it shifts perfectly well on a 11-32 it should have no issue shifting to a 25 tooth cog? Surely somewhere on the 11-32 cassette there exists a 24/26/26 tooth cog?

    By that logic you could have a 32-11 instead of an 11-32

    July 23, 2018 at 2:54 pm #923895
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    shmooster
    fukawitribe wrote:
    Anecdotal evidence from the ‘tubes suggest that GS derailleurs shift 25T cassettes just fine, even though not officially recommended.

    Anecdotal evidence from the tubes suggests lots of things 🙂

    It might work, so worth tweaking the B screw to bring it closer, but more likely to be sensitive to anything slightly off (chain length, bent hanger, dirty cassette or chain etc). Shimano wouldn’t go to the bother of having two different derailleurs without a reason.

    New derailleur not cheap, if the OP has an 11-28 lying around maybe worth a bash as a compromise?

    July 23, 2018 at 1:50 pm #923893
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    Anonymous
    shmooster wrote:
    If you’ve gone from 11-32 you must be on a GS derailleur, that has a minimum low sprocket of a 28, you’re running a 25 so really need an SS derailleur. You can try tweaking the B screw but you’re operating the derailleur out of spec.

    Surely if it shifts perfectly well on a 11-32 it should have no issue shifting to a 25 tooth cog? Surely somewhere on the 11-32 cassette there exists a 24/26/26 tooth cog?

    The issue is more than likely (as already mentioned) chain length. Given you have gone up two teeth in the small chainring and down 7 teeth in the laregest cog it would make sense that the chain lenght needs to be shorter than you had previously.

    July 23, 2018 at 11:54 am #923891
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    fukawitribe

    Anecdotal evidence from the

    Anecdotal evidence from the ‘tubes suggest that GS derailleurs shift 25T cassettes just fine, even though not officially recommended.

    July 23, 2018 at 10:14 am #923889
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    shmooster

    If you’ve gone from 11-32 you

    If you’ve gone from 11-32 you must be on a GS derailleur, that has a minimum low sprocket of a 28, you’re running a 25 so really need an SS derailleur. You can try tweaking the B screw but you’re operating the derailleur out of spec.

    https://bike.shimano.com/en-EU/product/component/ultegra-6870-di2/RD-6870-GS.html

    KMC chains are not directional (that I’ve seen anyway).

    July 23, 2018 at 9:21 am #923887
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    Russell Orgazoid

    Turn the chain around to run

    Turn the chain around to run the other way.it may be designed to run in one direction.

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