signalnc
07-18-07, 06:10 PM
what does the term "bcd" refer to when talking about chainrings?
Bicycle Mechanics - "bcd" term in chainring
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tellyho
07-18-07, 06:14 PM
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.
Scooper
07-18-07, 06:19 PM
Sheldon has a nice table for various old and new BCD standards for different manufacturers HERE (http://www.sheldonbrown.com/gloss_bo-z.html).
HillRider
07-18-07, 06:30 PM
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.
signalnc
07-18-07, 07:02 PM
ok-thanks for the info