144 BCD

A 144 BCD (Bolt Circle Diameter) is the traditional, track-specific standard designed specifically for single-speed and fixed-gear bicycles. It describes the dimensions of the spider used to bolt the chainring to the crank arm.

Because the circle is large, the minimum chainring size you can run on a 144 BCD crank is 42T (teeth). Sizes generally range from 44T to 56T or larger.