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  1. #1
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    Tangled Chain Puzzle

    Ok, I'm supposed to be smarter than this but I'm stumped.
    I took the wheels off this bike earlier this winter to use on another bike and stored the bike. Today, I went to put the wheel back on and the chain is tangled and I am at a loss as to how this is possible. I do have spare chain pins (it's a shimano chain) so I know I can easily just take the chain off and start over, but that would be admitting defeat. The picture shows the bike upside down. The chan actually crosses itself and is twisted (the upper chain crosses below the lower chain???) I'm a logical person with decent mechanical skills, and I just spent an hour on this puzzle and I cannot see how I can untwist this chain without removing it or taking the derailleur apart, yet I know I shouldn't need to do this. Obviously I am missing something and/or completely confused.
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    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  2. #2
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    First things first, carefully enlarge the figure eight loops, and guide them past each other to clear that tangle.

    Now for the RD -- don't start until you've the entire post, the important stuff is at the end.

    At a glance, your derailleur cage is rotated one full turn out of it's operating position. Looking at it from the camera's point of view, try rotating the cage clockwise, guiding the chain past the twist point until it clears.

    If that doesn't work for you, remove the lower (top in the photo) pulley screw, and loosen but don't remove the upper one. Remove the pulley, rotate the inner cage plate to free the chain, untangle the chain, and replace the chain, correctly routing it and replace the pulley. Note that the correct route is an "S" passing behind the lower pulley and in front of the upper one (when right side up). Be sure that the idler cage is rotated to have tension such that it wants to pull the lower pulley backwards.

    BTW- most derailleurs have a stop to prevent the idler cage from turning past a certain point. If yours still has this stop, the cage probably didn't rotate, and you can work out the puzzle simply by working out the twist without doing anything else. If your RD doesn't have this stop and the cage can rotate 360 degrees, you might be missing a small part, or have sheered off a stop tab. Either way the idler cage spring should be preloaded by turning the cage about 1/2 turn counter-clockwise (facing it from the right side of the bike) such that when released the lower pully springs backwards.

    Good luck. It's been my experience that clearing these tangles often goes faster with a few beers.

    Important, When I use the terms upper, lower, clockwise, etc. I'm speaking from a point of view from the right side of a right side up bike. That means everything will be backwards and upside down from your camera's perspective. You might find it easier if you hang the saddle over a pipe and work with the bike right side up, which is how you're most familiar with it.
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    The key to solving any problem is to understand and address the underlying cause.

  3. #3
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    Yep, that's the piece of the puzzle I was missing.
    It never occurred to me that the cage could rotate all the way around like that. It took me a whole 15 seconds to fix it once you pointed out the problem.

    Thanks.

    BTW. Mine does have the stop, but the tab sheered right through it (looks really soft).
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

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