Chain clipping front derailler

Discussion in 'Cycling Equipment' started by brian_biker, Aug 30, 2010.

  1. brian_biker

    brian_biker New Member

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    I have a 24 speed Trek 2400 MTB. My chain clips the front derailler under the following conditions:

    Middle chainring and last four smallest cogs.
    Large chainring and last three smallest cogs.

    The clipping noise under these conditions is distinct and obvious, I can see the chain clipping the right side of the front derailler. Attached are pictures showing the situation.

    This started happening about a day ago. I might have been pedaling too slowly and/or with too much pressure when shifting the main chainring, which might have caused it, but I am not sure at all.

    Should I take it in to the LBS or is it possible to fix it without being an expert bicyclist repairman? Thanks.
     
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  2. billydonn

    billydonn New Member

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    Sounds like you need more cable tension on the FD. Trace the cable that controls the FD up the line toward your handlebars and you should find a barrel adjuster somewhere (most likely on the shifter itself). Turn the barrel adjuster to make the cable housing longer. Assuming your outer limit screw is okay, this should fix you up. If you have bumped the entire FD out of kilter somehow you might need to tweak its attachment to the frame, which would be a complication.

    Derailer Adjustment-How To

    The LBS should easily be able to take care of this but it is good to learn how to do this yourself.
     
  3. brian_biker

    brian_biker New Member

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    Thanks for this great explanation and link. Let me try this. If I don't post back, assume all went well. :)
     
  4. brian_biker

    brian_biker New Member

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    I tried tightening the knob on the left shifter, which did indeed prevent the chain from clipping the front derailler while on the biggest chainwheel and smallest sprockets. However, at this setting the chain was clipping the FD on the middle chainwheel for most of the rear sprockets. Then I tried tightening/loosening/randomly tinkering with the outer/inner screws on the FD itself, which caused changes as to which gear settings caused the chain to clip the FD.

    Now, I am at the point where the middle chainring works fine (doesn't clip the FD on any rear sprocket setting), but the left shifter is so tight that I cannot shift the chain up onto the largest chainwheel! I really don't know what I am doing with the inner/outer screws.

    My goal is to make prevent the chain from clipping the FD on ALL gear settings, and be able to shift to all chainrings.
     
  5. billydonn

    billydonn New Member

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    It generally is not very realistic to expect to be able to use all gear combinations on a triple crankset. Using the big front ring and big cogs on the rear is called crosschaining and you should avoid it. Same with the small front ring and little outer cogs. On the middle front ring you might be able to use all rear cogs.

    Bad idea to turn those limit screws without understanding what they do. This is explained at Sheldon's and many other internet sites. It sounds like you have taken too many turns on the cable tension and then moved the outer limit screw so as to prevent the FD from going out as far as it needs to.

    Recommendation: Read FD adjustment internet instructions very carefully and then disconnect your cable at the FD and start all over again. Some video links are below along with another text explanation with pictures. OR take your bike to the LBS.

    How To Adjust Your Front Derailleur - Bicycle Tutor
    [ame=http://www.youtube.com/watch?v=nzSUaPYZsMw&feature=channel]YouTube - Bicycle Repairs : How to Fix Front Bicycle Dérailleur Gears[/ame]
    [ame=http://www.youtube.com/watch?v=ngm6dr-1na0]YouTube - 9 - Front Derailleur Adjustment[/ame]
    Park Tool Website
     
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