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  1. #1
    mtbr member
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    dropping my chain on my Kona unit

    Hello,

    I'd appreciate any help with this problem I've been having. I have a Kona Unit 29er frame that is a couple of years old. (purple model) Since I built the frame up I've had a consistent problem with the chain falling off. It happens when I'm pedaling hard through rough or rolling terrain. Usually when I am pedalling on and off. My rear wheel is a dmr hub/ dt swiss rim and an acs freewheel. The chainline seems straight and before each ride I tighten the chain. I've been running it tighter than I should have to and that seems to help keep the chain on but it usually still comes off at least once on my rides. A local friend who is a framebuilder seems to think that it is flex in the rear end at the bottom bracket ./ chainstay junction. The chainstays are welded to a piece of plate steel which is welded to a short piece of tubing then to the bottom bracket shell. I do notice how much flexier the rear end is compared to my Waltworks frame. Is this a problem with all these Kona frames, or is their another problem that I'm failing to diagnose?

    Jason

  2. #2
    meatier showers
    Reputation: Sparticus's Avatar
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    Quote Originally Posted by jason74
    Hello,

    I'd appreciate any help with this problem I've been having. I have a Kona Unit 29er frame that is a couple of years old. (purple model) Since I built the frame up I've had a consistent problem with the chain falling off. It happens when I'm pedaling hard through rough or rolling terrain. Usually when I am pedalling on and off. My rear wheel is a dmr hub/ dt swiss rim and an acs freewheel. The chainline seems straight and before each ride I tighten the chain. I've been running it tighter than I should have to and that seems to help keep the chain on but it usually still comes off at least once on my rides. A local friend who is a framebuilder seems to think that it is flex in the rear end at the bottom bracket ./ chainstay junction. The chainstays are welded to a piece of plate steel which is welded to a short piece of tubing then to the bottom bracket shell. I do notice how much flexier the rear end is compared to my Waltworks frame. Is this a problem with all these Kona frames, or is their another problem that I'm failing to diagnose?

    Jason
    What kind of chainring are you running? Is is possible that either your ring or your cog has a slightly bent tooth? That'll kick a chain off.

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  3. #3
    mtbr member
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    I'm running the stock 32 tooth chainring that came on my fsa v-drive singlespeed cranks. I'll check them both for bent teeth. thanks

    Jason

  4. #4
    Ovaries on the Outside
    Reputation: umarth's Avatar
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    I can think of a lot of reasons. I assume you have a SS specific cog/chainring that aren't worn to bits. You could have the rear wheel skewed slightly to one side, which can pop the chain off. Then there is Sparty's submissions.

    It also could be BB. If you don't mind the flex, then I'd consider getting a bashguard and chain watcher. Not really sexy SS options, but if it solves the problem...

  5. #5
    Mtbr Forum Sponsor - Homebrewed Components
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    do you have more wear on one side of the chainring than the other? if your chainline is off, it usually will polish/wear down either the inside or outside of the chainring, depending on which side the chainline favors. I know you said your chainline looks straight, but "looks straight" is often not good enough. If you're really having chainstay flexing issues, then i'd suggest having your chainline very slightly inboard in the rear (towards the hub). This way it'll be straighter when under torque.

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