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  1. #1
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    Front just won't shift consistently

    I'm in a bit of a situation that seems to be above my current mechanical aptitude, so I come to the altar of bikeforums to seek guidance. My gf has a ~2 year old Jamis Quest (1500 mi or so on it), all components still stock with front shifting that just won't stop sucking. According to her it's never been great but degraded just before she stopped riding in the winter. I consider myself passably acquainted with derailleur setup... I've built up bikes from scratch and maintain 4 in my stable and they all work great.

    Components:
    - 105 for STIs and Double band clamp FD
    - TruVativ Elita Compact 50/36

    Symptoms:
    - Difficulty shifting from little -> big. About half - 2/3 of the time it'll grind for 2-5 revolutions and finally pick up (with my hand holding in the lever the whole time). The other times the derailleur will move but the chain will just never pick up onto the big.
    - Tendency to drop chain on shifts in either direction.
    - Occasionally the lever will get "stuck" in the big position--it takes a tremendous amount of force (several times normal) on the small paddle to get it to let out cable again.

    The saga:
    I started out with adjusting the limit stop screws, and it seemed to shift fine in the stand. Back out on the road, however, and it goes to crap again. The cable was all frayed (apparently they were never capped by the shop) so I replaced that and re-adjusted limit screws and cable tension until it was fine on the stand. On the road test, it shifted great about a dozen times, and then back its old tricks. Taking a closer look, it seemed that the derailleur was mounted a couple mm too high, so I lowered, checked alignment and tried again. It seems that no matter what I try, I can't get the derailleur in a position where it'll consistently shift. The cables (but not housing) are new... it looks to my eye to be mounted straight and is within the spec'd 1-3mm of the top teeth... the levers look to be in good condition (and have definitely never been wrecked)... so any ideas what the heck is going wrong?

    Since I've fiddled with the derailleur to no avail, my suspicion is now on the lever. I think I might slap on a friction downtube shifter and see if that works fine. I've got some Shimano Exage (early 90s, I think) downtubes I could test out--would that test work, or has the pull ratio changed in the intervening years?

    Any other advice to try out?

    Thanks,

    Tyler

  2. #2
    Senior Member
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    Too much cable tension could account for the shifter refusing to shift from the big ring to the inner ring.
    Use the instructions at http://www.parktool.com for adjusting the shifting. Do all of the steps in proper sequence leaving nothing out. It is very important to have the shifter in its lowest position with all of the cable out when attaching the cable to the derailleur.
    You could also try flushing out both shifters with WD40.

    Al

  3. #3
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    It's also probably worth replacing the housing along with the cable.

  4. #4
    Senior Member
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    Quote Originally Posted by Mondoman View Post
    It's also probably worth replacing the housing along with the cable.
    Yes, always replace housings when replacing cables.

  5. #5
    Great State of Varmint Panthers007's Avatar
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    Oil the cable and drip some down the housing. Grease can harden and is best avoided.
    How do you keep an idiot in suspense?

  6. #6
    Your mom
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    +1 to following Park's instructions from beginning to end. You're basically un-installing and re-installing the FD. This is the ONLY way I've found to consistently solve FD problems in the least amount of time.

  7. #7
    1 bike 2 many. Butterthebean's Avatar
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    Quote Originally Posted by Al1943 View Post
    Yes, always replace housings when replacing cables.
    I have to call shenanigans on this statement. The housing is less than 2 years old. Unless it is crimped somewhere, it's probably fine...and I doubt it's causing this particular problem. As Panthers007 stated, a little lube down the housing helps alot, especially with ghost shifting.

    As for the OP, I would say this sounds like a cable tension issue....have you tried trimming the barrel adjusters slightly. And if the chain is being dropped, that is usually a matter of the high/low limit screws needing some adjustment.

    Sometimes things work differently on the work stand than they do under load.
    The internet gives you the opportunity to be an obnoxious jerk. But you are not obligated to do so.

    I see old people, but then they turn out to be my age.

  8. #8
    Senior Member oldbobcat's Avatar
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    Ditto on the limit screws. When the chain's on your innermost cogs, you need a bit of a gap with the inner cage plate so the spring can through the chain off the big ring. When the chain's on the outermost cogs you need a much smaller gap with the outer cage plate--large enough so the chain doesn't rub and small enough so as to prevent overshifting. Also be sure the cage is aligned so the outer plate is parallel with the chain in its outermost position. If downshifting is a problem, parallel with the chainrings is a kludge that might also work

    A most misunderstood front derailleur adjustment issue is cable tension. You need just enough to throw the chain onto the next ring from all rear cog positions. More than "just enough" is too much. With Shimano shifters this means the cable will have some slack when the derailleur is at its innermost position.

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