bcd on Middleburn duo chainrings- Mtbr.com
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  1. #1
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    bcd on Middleburn duo chainrings

    I am asking this question here since it pertains to my weightweenie-ness, lol.
    I would like to know the bolt circle diameter of the outer ring on the Middleburn duo chainrings. I didn't see it listed on their website. I want to know if I could use the outer ring on a FSA K-Force light 386 carbon crankset. The 386 crankset uses an 86mm bcd. Thanks!

  2. #2
    Hack Racer
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    If you have a DUO setup, you can only run the DUO rings. Because the spider is integrated into the small ring, and there is a step on the small ring that matches up with the big ring.

  3. #3
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    Quote Originally Posted by Cheers! View Post
    If you have a DUO setup, you can only run the DUO rings. Because the spider is integrated into the small ring, and there is a step on the small ring that matches up with the big ring.
    You have completely missed the point of my question entirely.
    I must've not explained well enough.

    Let me simplify:

    The outer ring on a Middleburn duo.
    What is the bolt pattern?

  4. #4
    Hack Racer
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    why don't you contact middleburn and find out?

    contact
    all enquiries

    matthew@middleburn.co.uk
    Phone: 01420 520223
    Fax: 01420 521142


    address

    Middleburn Components
    Unit 5 Bentley Park
    Blacknest Industrial Estate
    Blacknest
    Alton
    Hampshire
    GU34 4PX


  5. #5
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    Take a look at the duo chainring page:

    Middleburn bicycle components, cranks, chainrings, hubs and accessories

    The large chainring attaches directly to the crank via a splined interface, and not by chainring bolts. The small chainring then attaches to the large chainring.

    So even if the bolt pattern was the same on the middleburn and the FSA, you'd have to cut out the center spline section on the middleburn chainring in order to use it. That would probably leave it not as strong as it should be.

  6. #6
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    The large chainring attaches directly to the crank via a splined interface, and not by chainring bolts. The small chainring then attaches to the large chainring.
    That is actually backwards. On the Duo crankset it is the small inner ring that attaches to the crank arms with a center lockring and the larger outer ring is then bolted to the inner ring using 3 standard double chainring bolts.

    My Duo crankset BCD measured 82mm by way of both regular diameter and C-C*1.155.

  7. #7
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    I stand corrected! Well too bad the BCD doesn't match.

  8. #8
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    Oh well, they don't match. Thanks for measuring them! It was a good idea at least.

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