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  1. #1
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    front derailleur clamp size

    i am going to purchase a new XTR FD-M960 and am not sure what clamp size i need 31.8mm or 34.9mm, what do i need to measure to find out ? i tried to measure where my Alivio FD is but i didn't come up with either one of them measurments. sry im such a newbie.
    Last edited by rodman; 11-24-2005 at 01:53 PM.

  2. #2
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    Reputation: Bikinfoolferlife's Avatar
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    Measure the diameter of the outside of the seat tube where the fd clamps...usually same diameter at the top of the seat tube, too, so that might be easier for you to measure (with seat post out). Not all bikes are 31.8 or 34.9 either...
    "...the people get the government they deserve..."
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  3. #3
    All 26.5" all the time!
    Reputation: Zanetti's Avatar
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    If you're confident enough to properly re-install your current derailleur, the size is usually stamped on the inside of the clamp.

  4. #4
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    thanks guys, i believe i need the 31.8 size.

  5. #5
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    And I believe all the new shimano front derailleurs come in 34.9mm by default with shims to fit any of the smaller diameters.. I just got a new XT front last month and it's fitted with a shim for 31.8mm, grips very nicely cuz part of the metal shim is plastic rubber...

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