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  1. #1
    Senior Member 5kdad's Avatar
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    Double chain ring vs. compact

    What's the difference between a double chain ring and a compact chain ring?
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  2. #2
    Senior Member JTGraphics's Avatar
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    BBC on a Std road cranks double is 130mm compact is 110mm.
    This is distance from bolt to bolt center to center.
    It may not be fancy but it gets me were I need to go.
    http://www.jtgraphics.net/cyclist_bicycles.htm

  3. #3
    Senior Member
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    The BCD Bolt Circle Diameter for most modern cranksets, including Shimano are 130 mm. Compact cranksets have a 110 mm BCD and can accept smaller chainrings. Campagnolo standard cranksets have a 135 BCD.

  4. #4
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    Quote Originally Posted by Al1943 View Post
    The BCD Bolt Circle Diameter for most modern cranksets, including Shimano are 130 mm. Compact cranksets have a 110 mm BCD and can accept smaller chainrings. Campagnolo standard cranksets have a 135 BCD.
    Of course to complicate things the TA cranks on my bikes have a BCD (50.4 mm) that's less than half the size of the current 'compacts' but they're considered regular size.

    And to JTGraphics:
    No, the BCD is the diameter of a circle that would pass through the center of the bolts. The center-center distance between bolts is 76.4mm for a 130mm BCD and 64.7mm for a 110mm BCD.

  5. #5
    Senior Member tjspiel's Avatar
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    On the off chance you meant compact crankset instead of an individual chainring, the idea is to give you a lower/wider gear range without going to a triple. The size difference between the rings will be greater and the size of the rings themselves will be smaller than on a more standard double.

  6. #6
    Real Men Ride Ordinaries fuzz2050's Avatar
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    How about this, a compact crank usually has two chainrings,in the 48 and 34 range, while a standard usually has them in the 52 and 42 range. Give or take a tooth or two...

  7. #7
    Senior Member dstrong's Avatar
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    A "standard" road bike double is typically a 53/39. A "compact" road bike double is typically 50/34.

    2014 Specialized RoubaixOOOOOO 2003 Interloc ImpalaOOOOOO 2007 ParkPre Image C6 (RIP)


  8. #8
    rebmeM roineS JanMM's Avatar
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    A compact crankset is a double crankset. Not all double cranksets are compact cranksets. The cyclocross crank (46/38) on my hybrid is neither a compact not a standard road double.
    RANS V3 (steel), RANS V-Rex, RANS Screamer

  9. #9
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by prathmann View Post
    Of course to complicate things the TA cranks on my bikes have a BCD (50.4 mm) that's less than half the size of the current 'compacts' but they're considered regular size.
    And they make great "compact" cranks (43/30 in this case):

  10. #10
    30 YR Wrench BikeWise1's Avatar
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    Quote Originally Posted by JohnDThompson View Post
    And they make great "compact" cranks (43/30 in this case):
    Lyotard pedals!!!!

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