Chain fell to bottom bracket

Discussion in 'Cycling Equipment' started by Frinton, Mar 29, 2006.

  1. Frinton

    Frinton New Member

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    I have Ultegra and Dura-ace mix. Today I was spinning pretty fast in my big ring and 3rd tallest gear and for some reason I decided to downshift to my small chainring. The chain fell to the bottom bracket. For the rest of my forty mile ride, this did not happen again. Is this because I should have made that shift while spinning out the big chainring and bigger cog, while going to the small chainring? Any advice would be appreciated. When I returned home, I could not duplicate this, but would rather it not happen again.
     
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  2. free_rideman

    free_rideman New Member

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    Well first of all, when ever you shift the front gears (and kind of for the rear gears), you shouldn't be doing it at full output. You have to give the chain some time to actually shift, and not loading it with weight the whole time. If you do, then the chain will have too much speed and just "jump" over and fall off.


    But this problem also arises when running a double compact crankset, since the jump is greater than in a triple crankset setup. For these situations, you will either have to setup your derailleur to perform better, or buy a specific derailleur for compact cranksets.
     
  3. tourdelivermore

    tourdelivermore New Member

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    This will happen from time to time, even when the drive train is adjusted and running well. To get the chain back on the rings, simply shift the front derellieur to the big ring, then pedal slowly to "pick up" the chain on the big ring.
     
  4. yancy0303

    yancy0303 New Member

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    Your front derailleur has limit screws that need to be adjusted. Your mechanic can do it in about 3 seconds. the limit screws "limit" the movement of the derailleur not allowing the derailleur to move past a certain point.
     
  5. gclark8

    gclark8 New Member

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    While you are having the FD Low Limit Screw adjusted, yes the screws do bed in to the stops, ask the mechanic to check the chain length. It may be a link or two on the long side.

    Can you give us your Chainring sizes and rear cassette range. It may just be a little too much chain slack for the Rear Derailleur to take up (if a double), when down shifting to a 39t front when on a 13/14 tooth at the rear.
     
  6. Rayzor

    Rayzor New Member

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    There is a product called a fang chain keeper by Deda that will stop the chain dropping off. Regardless of how well my derailer was setup I always had problems. No more with this magic device.

    http://www.probikekit.com/display.php?code=K1108
     
  7. Cyclesafe

    Cyclesafe New Member

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    Sometimes, even if the front deraileur is properly adjusted, there are shifting situations when you will lose your chain to the bottom bracket. Such "suicide shifting" is most disconcerting while trying to mount a very steep grade and you are forced to chose between unclipping or trying to get the chain back on (usually to late).

    A real inexpensive insurance policy is a Jump Stop from N-Gear. You send Nick your address, he sends you one, you either send it back or send him 10 bucks.

    http://www.n-gear.com/
     
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