Chain hopped off

captainhastings
captainhastings Posts: 4
edited September 2010 in Workshop
I have a new defy 2 about 7 weeks old gears have been fine and I had it checked after 4 weeks anyway. Coming down a hill on the dual carragway yesterday I knocked it into top gear and it came off at the back. Caused me to throw quite a wobble but I stayed on and got on the verge.
Is the odd hop off to be expected as part of the course or do I need to head to you tube and look for high gear limit screw :)

Comments

  • father_jack
    father_jack Posts: 3,509
    Check both limit screws (front and rear) One way is to loosen inners and move deraillers by hand. If the cable plops off, then you need to adjust it. Once done reconnect inners, and spend a few minutes rapid shifting trying to get the chain to jump (you wouldn't normally shift so rapidly, just a way of testing)
    Say... That's a nice bike..
    Trax T700 with Lew Racing Pro VT-1 ;-)
  • dmch2
    dmch2 Posts: 731
    The chain angle can make a bit of difference too, although the rear derailleur normally solves that problem at the back.

    If you hit a bump at just the wrong moment that could have caused it to jump as well.

    The cables might have stretched a bit more - although stretched cables would mean it wouldn't go far enough rather than go too far (I think :? ).

    Is the shifting crisp and happy the rest of the time? If so the cable adjustment is fine.

    So that leaves the limit screws as Father Jack said. But only adjust by a very small amount (half a turn maybe) as it's easy to go too far and/or forget how much you've moved it or get confused which limit screw is which.

    Might be worth checking that nothing is bent - does the derailleur hang perfectly straight down?
    2010 Trek 1.5 Road - swissstop green, conti GP4000S
    2004 Marin Muirwoods Hybrid
  • RUFUSPHOTO
    RUFUSPHOTO Posts: 3
    Proper setup of a rear derailleur with the limiter screws. The screws do exactly what they are called, limit the derailleur from bringing the chain too far on the high and low gear, causing the chain to come off.
    These should be set up at the very beginning and should not have to messed with unless a new chain or cassette is installed.
    http://www.youtube.com/user/SRAMtech#p/u/9/38vdA5OOBxI
    2:30 in to the video.

    Also check to make sure that your chain is properly sized. For a Sram chain, remove the chain them install it on the big chain in both the front and the rear, not passing through the rear derailleur. Notice where the links connect then add two links to that. Remove excess chain links and install a powerlink.

    It is usually improper limiter screw adjustments during setup or too long of a chain.

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