Bicycle Mechanics - Front deraileur keeps throwing chain past big ring
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09-16-05, 03:45 AM
For some reason I cannot get my Ultegra 9 front derailleur dialed in. I've read Sheldon Brown's derailleur adjustment instructions, but can't get just right.
My problem is the shift to the big ring from the small ring is either extremely sluggish (hesitates like it won't catch), but then if I adjust it just a little it completely jumps past the big ring and drops the chain off the crankset towards the pedals. (I've already tightened up the chainring bolts so it's not a sloppy chainring shifting all over the place.)
I've been using the high gear adjustment on the front derailleur to alter the position of the outer plate of the cage. What am I doing wrong here?
09-16-05, 04:03 AM
Try going all of the way back to the very beginning.
Front derailleurs really aren't that hard to adjust, but they are sensitive to the order that you do everything because every adjustment that you make affects all of the other later adjustments. After reading your post, my guess is that your LOW gear limit screw is off and that is affecting your shifting onto the big ring. I haven't looked over Sheldon's instructions but I assume they are similar to the ones on the Park Tool website. If so try this:
Disconnect your shift cable from your front derailleur and completely repeat your derailleur adjustment starting with the position of the derailleur on the seat tube. Be sure to do every step in order and don't skip any steps. Usually that'll do it.
Clean and lubricate the derailure. Sometimes they get sticky and don't respond well to the adjustments.
09-16-05, 07:12 AM
What is your technique for making the small-to-big upshift? If you are just "flicking" the upshift lever, you have to set the high gear limit screw out too far to get it to shift at all and the chain will spill periodically. If you shift by moving the lever against the stop and holding it there for a crank rotation or two, the shift is more positive and the limit screw can be set closer.
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