KONA UNIT chain tension help- Mtbr.com
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  1. #1
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    KONA UNIT chain tension help

    Hi Bikers
    I have a new unit and the chain tension varies massively from tight to loose
    during each rotation of the cranks.
    My bike shop cant fix it, they have had three goes.
    Does anyone have any experience with this ?
    Any other unit owners with the same or no problem ?
    I would really appreciate some help.
    Cheers
    Jeff

  2. #2
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    Is it always tight and loose in the same crank position?

    Maybe it's a wrong chain line lifting the chain up a bit getting tension in it.
    That's what I had once, but that wasnt on a stock bike

    Sent from my ONEPLUS A6003 using Tapatalk

  3. #3
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    Yep , always in the same spot.
    thanks for your reply.

  4. #4
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    You could check how tight the chain is on the cog or chainring. It should have a little play left to right (very little play).

    If the play is only to the right or left, the chain is being pulled towards a side

    Sent from my ONEPLUS A6003 using Tapatalk

  5. #5
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    Thanks ,Ill have a go.

  6. #6
    Armature speller
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    Straight edge held on the seat tube to out near the chainring teeth and turn the cranks to check if the chainring is properly circular.
    Similar with the rear cog.
    My Unit with XT cranks and an oval ring is tighter on the left power stroke.
    The chainring holes on the cranks are slightly out of spec.

  7. #7
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    Which cranks do you have? In my experience, most cranks are not completely concentric, and race face with the cinch mount are the worst.

    You can remove your chain and spin the crank while watching the ring against the seat tube for high/low spots.

    If your ring is bolted, you can follow Sheldon Brown's procedure for centering chain rings.

    This relatively common though, and I would just run my chain a bit tight in the tight spots if I couldn't improve it at all.

  8. #8
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    Thanks guys for your help.
    They have replaced the hub body too with no luck.
    Have checked chain ring for round as suggested and its perfect.
    Maybe the chain is stretched unevenly ?

  9. #9
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    Me er heard of a chain that is stretched that unevenly.

    But on the other hand a KMC X1 isn't too expensive to try

    Sent from my ONEPLUS A6003 using Tapatalk

  10. #10
    Downcountry AF
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    Quote Originally Posted by TenToes View Post
    Thanks guys for your help.
    They have replaced the hub body too with no luck.
    Have checked chain ring for round as suggested and its perfect.
    Maybe the chain is stretched unevenly ?
    This is very common on most singlespeeds (and also present on most geared bikes but nobody notices because of the derailleur). Manufacturing imperfections on the crank, spider, chainring, cog, etc. cause a tight and loose spot in the crank rotation.

    Just set your chain based on the tight spot and ride it. You can try to get rid of it a little by moving the chainring (assuming a 4 bolt), but it should not cause any issues and you won't notice it.

    Many of us run an oval chainring which also causes a tight and loose spot every rotation. It's not a problem and works just fine.
    Rigid SS 29er
    SS 29+
    Fat Lefty
    SS cyclocross
    Full Sus 29er (Yuck)

    Stop asking how much it weighs and just go ride it.

  11. #11
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    You can also check the cog for concentricity the same way basically.

    Something is causing the chain length the grow and shrink, or your chain has a stiff spot.

  12. #12
    PEK
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    Hi.

    I had exactly same problem with my kona unit 2018.
    Front chainring is not centered correcly on FSA Comet Modular crankset. Mine had few millimeters ofset. You need special tool(expensive) to remove chainring and try to center it.
    OR better...buy differend brand crankset with 4 bolt chainring attachment.
    I used:
    Shimano
    SLX 11-speed Crank FC-M7000-1 175mm
    SLX 11-speed Chainring SM-CRM70 32T for FC-M7000-1
    XT Hollowtech II Bottom Bracket BB-MT800
    But you need also 11 speed chain and 11 speed compatible rear Sprocket.

  13. #13
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    Quote Originally Posted by PEK View Post
    I used:
    Shimano
    SLX 11-speed Crank FC-M7000-1 175mm
    SLX 11-speed Chainring SM-CRM70 32T for FC-M7000-1
    XT Hollowtech II Bottom Bracket BB-MT800
    Mine does it with XT cranksets on my Unit and Chameleon.

    Quote Originally Posted by PEK View Post
    But you need also 11 speed chain and 11 speed compatible rear Sprocket.
    Not if you're running it single speed.

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