Chainline diagnosis - front derailleur rub
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  1. #1

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    Chainline diagnosis - front derailleur rub

    I had my LBS swap my Ultegra components over to a new (used) frame. They installed a new BB, dura-ace headset, and SRAM 9-speed cluster, along with my ultegra crankset, a used braze-on Campy Record front derailleur, and my Ultegra STI shifters.

    They did a pretty shoddy job. I should have checked the quality of their installation at the shop, but when I got home and clipped in the cranks were loose. I broke out my tools, tightened things back together, checked out the shifting and lo and behold, have a significant case of chain rub on the inside of the front derailleur when on the small ring, big rear cluster. Arrrgh!

    I tried to use the limit screws on the derailleur to erase the rub, but it's at the limit. Rear shifting works fine.

    My diagnosis is a bad chain line. Can I solve this myself by trying to align the BB to move the chain wheels out, to the right, or might I have a mis-sized BB? One thing is for sure, this is not going back to the first LBS for a solution.

    The bike is rideable, just not in the two or three lowest gears. No problems on the big ring, but I am a small ring spinner and can't tolerate the loss of my three lowest hill gears.

    I think I'm talking myself into trying another LBS. Grrr.

  2. #2
    NeoRetroGrouch
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    Quote Originally Posted by Cape Cod Dave
    I had my LBS swap my Ultegra components over to a new (used) frame. They installed a new BB, dura-ace headset, and SRAM 9-speed cluster, along with my ultegra crankset, a used braze-on Campy Record front derailleur, and my Ultegra STI shifters.

    They did a pretty shoddy job. I should have checked the quality of their installation at the shop, but when I got home and clipped in the cranks were loose. I broke out my tools, tightened things back together, checked out the shifting and lo and behold, have a significant case of chain rub on the inside of the front derailleur when on the small ring, big rear cluster. Arrrgh!

    I tried to use the limit screws on the derailleur to erase the rub, but it's at the limit. Rear shifting works fine.

    My diagnosis is a bad chain line. Can I solve this myself by trying to align the BB to move the chain wheels out, to the right, or might I have a mis-sized BB? One thing is for sure, this is not going back to the first LBS for a solution.

    The bike is rideable, just not in the two or three lowest gears. No problems on the big ring, but I am a small ring spinner and can't tolerate the loss of my three lowest hill gears.

    I think I'm talking myself into trying another LBS. Grrr.
    If it's the right BB (2x or 3x) inside chainline should be fine. The normal problem with chainline is that the chain hits the large ring when on the small cogs.

    1 - Are you setting the limit screw with the cable disconnected?

    2 - Will a Campy FD work with your set up? (A little help here.)

    TF
    "Don't those guys know they're old?!!"
    Me, off the back, at my first 50+ road race.

  3. #3

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    I'll dick with the low range setting with the cable detached.

    I thought front derailleurs were ecumenical when it came to two-rings. I'll try the cable-free adjustment, give up and go to another LBS if that doesn't work.
    dc

  4. #4
    NeoRetroGrouch
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    Quote Originally Posted by Cape Cod Dave
    I'll dick with the low range setting with the cable detached.

    I thought front derailleurs were ecumenical when it came to two-rings. I'll try the cable-free adjustment, give up and go to another LBS if that doesn't work.
    dc
    Campy FD could be fine. I just don't know, so would ask - TF
    "Don't those guys know they're old?!!"
    Me, off the back, at my first 50+ road race.

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