Thread: On crank arms and BCD
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Old 04-15-15 | 09:37 AM
  #6  
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ThermionicScott
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From: CID

Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers), All-City Space Horse (hers)

You seem to be getting the bolt-circle diameter confused with the crank length. They have nothing to do with each other. Nothing!

The BCD determines the smallest chainrings you can run, and that is a factor in the gearing you want on your bike. Larger BCDs are used for more crank/chainring stiffness.
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