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  1. #1
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    cure for chain suck

    Hi,

    I have all new components, but on every ride I get chain suck: the chain runs back over on itself and gets jammed in the front derailleur and/or part of the chain gets wedged between the small ring and the chain stay. I almost fell over once on a steep hill when the chain jammed. I barely managed to squirm my foot out of the cleat and get my foot down.

    I soaked the chain in degreaser and relubed it, and the drive train was silent and felt slick, but I got chain suck again.

    Thanks.

  2. #2
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    Check your chain for a tight link. Chainsuck can be very damaging to you bike (and body).

  3. #3
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by Al1943 View Post
    Check your chain for a tight link. Chainsuck can be very damaging to you bike (and body).
    Probably not a tight link. A tight link will make the rear derailer hop but it won't cause chain suck.

    It's a damaged tooth on the inner chainring. Check for a tooth that is twisted or has a burr on it or is otherwise damaged.
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    Quote Originally Posted by cyccommute View Post
    Probably not a tight link. A tight link will make the rear derailer hop but it won't cause chain suck.

    It's a damaged tooth on the inner chainring. Check for a tooth that is twisted or has a burr on it or is otherwise damaged.
    A tight link can definitely cause chain suck. The chain can ride up the back side of the chainring instead of releasing in a flat path. When a tight link hits the rear derailleur and fails to go through the RD can be twisted right off the bike. It happened to a friend's new Trek, the dropout plate was twisted out of the chainstay requiring a trip back to the Trek factory.

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    I was having a chain suck problem. Replaced my chain, though it wasn't worn. Problem stopped.

  6. #6
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    It's possible that this is due to cross chaining (using the smaller sprockets with the small chain ring).

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    A chain can also be thrown by shifting the front and back simultaneously. But that's not "chainsuck".

  8. #8
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by Al1943 View Post
    A tight link can definitely cause chain suck. The chain can ride up the back side of the chainring instead of releasing in a flat path.
    Highly unlikely. A tight link will go around the chainwheel or pulleys standing away from the radius of the gear. That's why it slips on the pulleys and the cassette. If the link were tight enough to catch on the chainwheel and be sucked into the chainstay, it would be too tight to engage the chainwheel teeth and would stand off the teeth leading to slippage...not to catching.

    A burr or damaged tooth, on the other hand, engages the chain quite readily but won't disengage so that the chain is carried up into the chainstay.

    Quote Originally Posted by Al1943 View Post
    When a tight link hits the rear derailleur and fails to go through the RD can be twisted right off the bike. It happened to a friend's new Trek, the dropout plate was twisted out of the chainstay requiring a trip back to the Trek factory.
    This is not 'chain suck' in the classic sense.
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  9. #9
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    Chainsuck by definition is when the chain gets sucked up the back side of a chainring. Of course this can happen from a bent tooth, but it happens more often from a tight link in the chain, usually at the pin where the chain was joined.

  10. #10
    Elitist Troglodyte DMF's Avatar
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    Quote Originally Posted by helpless View Post
    I have all new components
    What new components? And why?

    New Posters - please READ THIS




    Well, buy chains that don't suck.
    Stupidity got us into this mess - why can't it get us out?

    - Will Rogers

  11. #11
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    Quote Originally Posted by Al1943 View Post
    Chainsuck by definition is when the chain gets sucked up the back side of a chainring. Of course this can happen from a bent tooth, but it happens more often from a tight link in the chain, usually at the pin where the chain was joined.
    exactly. this used to happen to me on my former 1x9 setup until i did two things: replaced the chainring with a proper rampless-pinless ring, and replaced the chain with a new properly installed and link-happy chain. Later, without much surprise, i discovered that the chainring did reduce instances of chainsuck, but that it happened on occasion (minor cross-chaining on a stiff link will "suck" the chain off the chainring from its underside). Those occasions were always after i had discovered (or created?) a stiff link in my chain. Heuristic as it may be, i discovered a properly functioning chain (i.e., no stiff links) meant no chain suck in my case.

    The most obvious solution is to eradicate cross-chaining, since a stiff link will still function (albeit not optimally) without coming off—given a perfect chain line.
    No slogans, just 14 facts.

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    coprolite fietsbob's Avatar
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    Used to be a great widget that fitted under the chainstay and filled in the gap between there and all 3 chainrings , so the Suck had no where to go.
    chain minders inside and outside disc chainguards are nice things..

  13. #13
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by Al1943 View Post
    Chainsuck by definition is when the chain gets sucked up the back side of a chainring. Of course this can happen from a bent tooth, but it happens more often from a tight link in the chain, usually at the pin where the chain was joined.
    I've had plenty of experience with chain suck. Any mountain biker has. I've never had a chain suck incident because of a stiff link. I've had plenty of stiff links after the chain was sucked up into the chainstay. Changing to a steel inner ring (I've never experienced chain suck on any other ring but the smallest inner one) mitigates the problem because the steel ring is more difficult to damage. Soft aluminum inner chainrings are almost guaranteed to cause the problem because at the high torques the small rings experience, the teeth are easily damaged.

    helpless describes a classic mountain bike chainsuck situation...high torque, steep hill, using the inner ring. Every single one of those I've ever experienced has been because of a damaged chainwheel caused by a previous botched shift.
    Last edited by cyccommute; 06-24-10 at 07:53 AM.
    Stuart Black
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  14. #14
    Listen to me powers2b's Avatar
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    Quote Originally Posted by cyccommute View Post
    It's a damaged tooth on the inner chainring. Check for a tooth that is twisted or has a burr on it or is otherwise damaged.
    ^^This.
    I've seen it many times on worn out rings (from running an old chain). As the teeth wear they produce a burr.
    Run a file along the rings to clear any burrs.

    Enjoy
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    Real Men Ride Ordinaries fuzz2050's Avatar
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    It's likely either a damaged inner chainring, or simply worn components. Either way, replacing the inner chainring and chain should hopefully solve your problem. When you do it, take a look around the bottom bracket shell to make sure it didn't cause any damage.

  16. #16
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    Make sure your chain is not too long, and try not to shift in the front when you're cross chaining. Better yet, don't cross chain. If you have a new rear derailleur, then the spring should be more than strong enough to take up the extra when downshifting on a nominally-sized chain. It should be just long enough to shift into big-big (aka 1-3 or "stupid gear"). Any longer and chain suck can become an issue with a triple crank.

  17. #17
    Unobtanium-Based Lifeform calamarichris's Avatar
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    Quote Originally Posted by DMF View Post
    What new components? And why?
    My best cure for chainsuck has thus far been avoiding SRAM.
    Works like a charm.

  18. #18
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    The main cause of chainsuck is insufficient chain tension - one of the RD's job is to maintain enough tension to avoid letting the chain get pulled up in the front. Bent teeth, stiff links etc will be contributors (as well as net results), but at the start most of the issues are caused by low chain tension - which explains why it almost always happen when you're close to the small-small cross-chain combo. And of course it's much more frequent on mountain bikes because the chain has to accomodate larger gear differences, and the banging around coming from the terrain will already want to throw the chain all over the place.

    So:
    1. Ensure your chain is sized correctly - not too long
    2. Ensure your RD is tensioning the chain correctly (beware of beat-up RDs with weak springs)
    3. Don't crosschain in the small chainring, specially on rough terrain.

  19. #19
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    I just wanted to bring this thread back to say that in my case, it is most likely burr on one of the teeth of the big ring. After reading this thread to find out why my bike has started having this problem all of a sudden, I went over and checked my front chain ring. There are a few teeth on the big ring, just behind the crank arm, that have some significant burrs on them . I don't have a file to deal with the problem right now, but I'll take it in or go buy a file.

    Thanks.

  20. #20
    bike whisperer Kimmo's Avatar
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    You can also take the burrs off with a sharp knife.

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