Viewing 20 posts - 1 through 20 (of 20 total)
  • Rubbing bits. 12 speed
  • howsyourdad1
    Free Member

    Righto, i’m a bit confused.

    12 speed set up.which I’ve never really got on with. Always something.

    Anyhow, this time it’s quite weird. Bike is fine in the stand, goes through the gears fine. When i am on the bike however, when i put power down i hear a strange ppr-ppr-ppr noise 🐈 and i can feel vibrations through the pedals. Seems to happen on the drive side. Almost like the chain is rubbing on the bottom jockey wheel.

    It is not the chain length, the chain is routed correctly, i have played with btension, clutch tension, changed to a new mech, checked the mech hanger is straight.  I’m at a loss for ideas!

    tthew
    Full Member

    Have you changed any bits? New chain not running on old chainring or jockey wheels properly for example.

    Or that old chestnut of the chain routed round the wrong side of the tab on the derailleur arm, (although that’s usually obvious on stand).

    coatesy
    Free Member

    Could be so many things, maybe not even the drivetrain itself. Broken axle, collapsed hub/freehub bearings, and BB bearings are some of the things that spring to mind when noises only occur under load.

    avdave2
    Full Member

    Or that old chestnut of the chain routed round the wrong side of the tab on the derailleur arm, (although that’s usually obvious on stand).

    I believe it’s possible to do this and ride 20 miles without really noticing. At least that’s what I’m told, obviously it’s not from personal experience. 🙂

    tthew
    Full Member

    I believe it’s possible to do this and ride 20 miles without really noticing.

    No, I can’t believe anyone would be such a daftie. 😜

    sillyoldman
    Full Member

    FS bike with upper guide – chain clears guide in stand, but not at sag point?

    the00
    Free Member

    Sounds very likely to the the chain routing through the derailleur. On M8000 11sp I ran in like that for 100s of km.

    howsyourdad1
    Free Member

    It’s not the chain routing through the mech, cheers though

    theotherjonv
    Full Member

    I misread the title, I thought you were overexcited by your new Eagle groupset……

    howsyourdad1
    Free Member

    Found a loose pivot bolt and have played more with b tension. Better but still not great. May just go back to 10 speed

    twohats
    Free Member

    Could be chainring wear.
    It takes very little wear on 12 speed chainrings for the chain to not release from the teeth on the bottom run under power.
    You can check by having the brakes on, driveside crank at 3 o’clock, all your weight on the pedal and reach down and pull the chain away from the bottom run, if it sticks slightly, that’s your noise.
    I’ve had two new chainrings do this in under 3 months each with new chains.

    HoratioHufnagel
    Free Member

    On my Shimano 12 speed stuff, sometimes the chain comes off the bottom jockey wheel and gets dragged through the gap between the jockey wheel and the cage.

    alpin
    Free Member

    I find anything above 10 speed is so much more finicky to set up and more sensitive to any knocks or adjustments.

    Give me a ten speed cassette with a wide range. Not fussed about the bigger jumps when off road or going down hill.

    chrisdw
    Free Member

    When you say you’ve played with the B tension. Have you used the appropriate tool (SRAM) / guideline on inside of cage (Shimano) to set it at sag? It really is that fussy.

    If it’s SRAM, is the chain meshing correctly with the narrow wide jockey wheel?

    If it’s all setup right I would be putting it down to chainring/chainline. Does it happen in all gears or just the extremes? 12 speed setups can introduce some pretty crazy chain angles which can cause noise when meshing with the narrow wide chainring.

    icyseanfitz
    Free Member

    I had an issue like this driving me nuts for ages, turned out the q factor of my cranks wasn’t correct so every time I put power into the left crank it ever so slightly contacted the chainstay and gave me a very weird “knock” feeling/noise up through the frame.

    thols2
    Free Member

    Frame flexing under power and tyre rubbing on chainstay?

    howsyourdad1
    Free Member

    will try the chainring thing ta

    nickc
    Full Member

    While I’ve found that 12sp outlasts pretty much everything I used before, I have found that jockey wheel wear is higher than before, and I check them more frequently than I used to

    The other one to check is if you have a quick link on the chain, whether it’s installed correctly. I had a annoying vibration (that sounded like your Brrr Brrr noise) that only really affected the 11T and 12T on the cassette, and eventually tracked it down to the quick link being upside down…

    rhayter
    Full Member

    I had a very similar thing on my previous bike, running GX Eagle. Turned out to be the bastard chainring. A new one – steel, not alloy – totally fixed it.

    peekay
    Full Member

    I had something similar, and it was my front top chain device rubbing against the chain when the chain was under tension. Have you ruled that out?

Viewing 20 posts - 1 through 20 (of 20 total)

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