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  1. #1
    Senior Member
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    "bcd" term in chainring

    what does the term "bcd" refer to when talking about chainrings?

  2. #2
    Your mom
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    Bolt Center Diameter. Literally, if you were to draw a circle through the center of the chainring bolts, the diameter of that circle is the measure referred to. Usually specific to a manufacturer. Easier to research what goes with your crank than to try and measure yourself.

  3. #3
    Decrepit Member Scooper's Avatar
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    Sheldon has a nice table for various old and new BCD standards for different manufacturers HERE.
    - Stan

  4. #4
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    Four 4-bolt chainrings the BCD is easy to measure, just measure the distance across two opposing bolts. For 5-bolt cranks it's not so straight forward so the usual method is to measure the distance between two adjacent bolts and look up a conversion chart such as Sheldon Brown's.

  5. #5
    Senior Member
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    ok-thanks for the info

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