Chainrings

The number of teeth on a chainring, in combination with a choosen rear cog, determine how hard a given gear will be. In order to select the proper chainring, it is necessary to know how the chainring mounts to the crank. Some chainrings attach by 4 or 5 bolts to a cranks spider. The distance between the bolts is referred to as the Bolt Circle Diameter, or BCD. You must select a chainring which matches the BCD of a crank.

Other cranks use direct-mount chainrings. Instead of mounting to a spider, the chainring, as the name implies, mounts directly to the crankarm and is secured by a locknut.

Chainrings for 1x use generally come with specially profiled, taller "narrow-wide" teeth which help improve chain retention. Chainrings for 2x and 3x systems, on the other hand, are generally engineered with ramps and pins to allow the chain to shift more easily from chainring to chainring.