Bolt Circle Diameter (BCD)

What is BCD?

BCD is an acronym for Bolt Circle Diameter.  It’s the measurement (diameter) of an imaginary circle passing through the centers of all the bolts in a round pattern – like chainring bolts that hold the rings to the crank.  On some cranks, like 4 bolt cranks, it’s fairly easy to measure, but for road and cyclocross with 5 bolts, it’s not so easy.  Here’s the cheat sheet. More