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Old 12-04-10, 06:14 PM   #1
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FD won't shift to large chainring when seated!

I have a triple chainring. Went out for a ride after weeks of not riding (cccoooollldddd!). The FD just didn't want to shift to the largest ring when I was on it. But shifts fine when I am off it. I am stumped on this one.
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Old 12-04-10, 06:27 PM   #2
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Only explanation I can think of is a reduction in cable tension as the frame flexes from body weight.. If this is what's happening then you need to add a bit of tension to the front derailleur cable.
Otherwise check the high limit screw, you may need to back it out a small amount.
Depending on what type of shifters you have it may be possible that all of the cable was not out of the shifter (or slack in the cable) when the cable was attached to the derailleur, but I think this is less likely.
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Old 12-04-10, 06:28 PM   #3
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could be the cable binding on something that's freezing inside the shifter housing.
I'm assuming you don't ride it inside the house and put it on the stand outside.
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Old 12-04-10, 06:30 PM   #4
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How heavy are you!!!!!!

Seriously, just to clarify, are you saying it shifts OK in the stand, but not while riding?

If so, it's fairly common. First try shifting while riding but with minimum pedal pressure and see if that makes a difference.

Getting the cage to move further out for crisp upshifting involves either or both of two adjustments. You have to determine whether the cable isn't moving it far enough or if the outer limit is restricting it too much. Hop back onto the bike and thy shifting by pulling the bare wire away from the frame. If that makes a difference, then your cable needs to be pulled a bit tighter. This is easy if you have a barrel adjuster on the lever on in-line, otherwise loosen the pinch bolt and pull some cable down (shift to the inner first, so you're not fighting the spring).

If it won't shift even if you pull on the D/T wire back off the limit a hair, and try again. Once you have it shifting well using the "override" then see if it's OK by lever. If not reset the cable tension as I described earlier.
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Old 12-05-10, 12:52 AM   #5
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Thanks for the replies.
The H limit screw is loose. The cage can't go any further.
How do I compensate for cable tension with me seated? It never happened before.

Can this be considered as chain suck?
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Old 12-05-10, 10:46 AM   #6
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Did you try shifting by pulling the wire from the frame, while riding? How did that work out?
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Old 12-05-10, 12:25 PM   #7
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This is not chain suck. Chain suck is when the chain gets stuck on the bottom of a chainring and gets jammed between the frame and chainrings.

It is also unlikely this is cause by frame flex changing cable tension unless your frame is made from balsa wood and cornflakes.

Go to Parktool.com and follow their derailleur setup instructions step-by step. Front derailleur alignment and height are very very important.
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Old 12-05-10, 01:41 PM   #8
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When the chain is on the smallest chainring is there any slack in the cable? There should not be. Slack can be removed at the cable fixing screw on the derailleur. If you try removing slack here be careful to reattach the cable with the correct cable routing.

You should be able to add cable tension with a barrel adjuster at the end, sometimes in the middle, of the cable housing. Usually a counter- clockwise turn of the barrel adjuster lengthens the housing, adding tension by forcing the cable to take a slightly longer route.
It should not take much of a change.
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Old 12-05-10, 02:22 PM   #9
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Quote:
Originally Posted by Al1943 View Post
When the chain is on the smallest chainring is there any slack in the cable? There should not be. Slack can be removed at the cable fixing screw on the derailleur. If you try removing slack here be careful to reattach the cable with the correct cable routing.

You should be able to add cable tension with a barrel adjuster at the end, sometimes in the middle, of the cable housing. Usually a counter- clockwise turn of the barrel adjuster lengthens the housing, adding tension by forcing the cable to take a slightly longer route.
It should not take much of a change.
+1 My first thought was cable stretch, which would make it a bit slack when on the small ring.
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Old 12-05-10, 05:55 PM   #10
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I found the source of my problem.
When the bike was on the hanger stand, I think the FD cable was kinda snagged. Not until AL1943's comments that I clued in.
Brought the bike down on the grown, loosen the FD's pinch bolt and re-tighten the cable.
Works again!
Thanks all!!!
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Old 12-05-10, 09:14 PM   #11
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For anyone else having FD issues I have found these how-to-do to be pretty good. The one on FD tuning may help eliminate the obvious.

http://video.bicycling.com/playlist/...ke-Maintenance

Folks might also check to see if there is any dirt or ?? in the hole in your frame where the FD cable passes through. With my bike I seem to keep getting dirt in the cable hole that causes binding shifting problems.
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