Home Forums Bike Forum 12 Speed Chain Length – Confusion

Viewing 16 posts - 1 through 16 (of 16 total)
  • 12 Speed Chain Length – Confusion
  • simono5
    Free Member

    Hi everyone,

    So I’m building my first full sus frame up with a new Shimano XT (M8100) 1 x 12 drive train.

    Built a few hardtails up in the past with 1 x 11 but really struggling with the 1 x 12 and getting the right chain length.

    I’ve used page 13 of this document as a guide;

    https://si.shimano.com/en/pdfs/dm/MARD001/DM-MARD001-04-ENG.pdf

    But the chain is terribly baggy when on the highest gear.  I’m totally lost and the more I search the more confused I get.

    Any advice on getting the correct chain length would be greatly appreciated as following the Shimano guide isn’t getting anywhere close to the results I need.  Thank you.

    IMG_20231031_203135IMG_20231031_203128

    Show us a picture of how the mech looks in the biggest sprocket

    simono5
    Free Member

    Thank you, shots of highest and lowest.

    IMG_20231031_205901IMG_20231031_205744

    Is that a long cage mech? Also, is your chain sat on your chainstay in the highest gear??

    bikerevivesheffield
    Full Member

    Have you sorted b tension 

    simono5
    Free Member

    Yes, it’s a long cage, I bought the 1×12 upgrade kit here;

    https://r2-bike.com/SHIMANO-Deore-XT-Upgrade-Kit-M8100-1×12-speed-Cassette-10-51-Teeth

    Yes, the chain is sat on the chainstay in the highest gear 🙁

    davros
    Full Member

    I’ve had this before, followed instructions to set length and it was too baggy, just took two links out then it was spot on.

    Have you sorted b tension

    That was going to be my next question

    If that’s ok, them you can probably/definitely get away with taking a link out.

    Not sure that’s going to sort your chainstay issue though, unless it’s just the sag that’s making it sit on there 

    bikesandboots
    Full Member

    FlareMAX? Ask Cotic. Then you’ve eliminated length as a potential cause and can focus on adjustments.

    bigfoot
    Free Member

    had similar when i went AXS and also swapped to a 52 tooth cassette. set length as per sram instructions and was very slack, ended up taking 2 links out to sort it. removed shock to check it allowed full travel in the 52 tooth and its been fine for the last 10 months.

    Daffy
    Full Member

    Isn’t the chainstay problem going to even worse once you’re sat on it?

    davros
    Full Member

    For comparison my gen4 flaremax with slx12 speed mech, xtr cranks. Looking again at your 4th image, it doesn’t appear too baggy as there is tension keeping the mech forward.

    PXL_20231101_080100221PXL_20231101_080326387

    martinhutch
    Full Member

    EDIT: Forget that, I thought they were talking about chain clearance not chainring clearance.

    b33k34
    Full Member

    I’ve had real trouble with 12S and long cage mechs on suspension bikes.  It’s a very fine line between baggy as hell in bottom gear and stupidly tight in top (which reminds me that I need to look at K’s as it seems too short now)

    rootes1
    Full Member

    yep next as a few have already mentioned above is to set the B adjust using the marks on the back of the cage, you will probably find the mech needs to move quite a bit further out and this will take up a little bit more slack.

    Page 23 on in that guide: https://si.shimano.com/en/pdfs/dm/MARD001/DM-MARD001-04-ENG.pdf

    5
    simono5
    Free Member

    Thanks everyone for there support and ideas on this.

    I decided to take the derailleur off and start again.  This quickly flagged my error and stupidity.

    Simply, I had the stopper that is part of the derailleur for the B Screw not sitting in place.  So the B screw was hitting the frame stopper and not the derailleur stopper.

    All good now and a step closer to riding.

    Thanks again for your help.

    1x12

Viewing 16 posts - 1 through 16 (of 16 total)

You must be logged in to reply to this topic.