A bicycle crankset, which is adapted to connect to a chain , comprises: a chainring having a round circumference and a plurality of teeth on the circumference to engage the chain, wherein the chainring has a chainring center , which is a center of the circumference , and a connecting portion ; the chainring having a plurality of connecting bores of a first noncircular motion path on the connecting portion , wherein the connecting bores of the first noncircular motion path have a center of rotation, and the center of rotation of the connecting bores of the first noncircular motion path is kept a distance from the chainring center ; the chainring having a plurality of connecting bores of a circular motion path on the connecting portion , wherein the connecting bores of the circular motion path have a center of rotation, and a location of the center of rotation of the connecting bores of the circular motion path is the same as the chainring center ; and a crankarm having a plurality of connecting arms at an end thereof, and an axial bore at the end having the connecting arms , wherein the crankarm has a center of rotation at a center of the axial bore , each of the connecting arms has a bore , and distances between centers of the bores and the center of rotation of the crankarm are the same; wherein the connecting arms of the crankarm are selected to be secured to the connecting bores of the first noncircular motion path or the connecting bores of the circular motion path of the chainring ; the chainring provides a first noncircular path of motion when the connecting arms of the crankarm are secured to the connecting bores of the first noncircular motion path, and the chainring provides a circular path of motion when the connecting arms of the crankarm are secured to the connecting bores of the circular motion path. a chainring having a round circumference and a plurality of teeth on the circumference to engage the chain, wherein the chainring has a chainring center , which is a center of the circumference , and a connecting portion ; the chainring having a plurality of connecting bores of a first noncircular motion path on the connecting portion , wherein the connecting bores of the first noncircular motion path have a center of rotation, and the center of rotation of the connecting bores of the first noncircular motion path is kept a distance from the chainring center ; the chainring having a plurality of connecting bores of a circular motion path on the connecting portion , wherein the connecting bores of the circular motion path have a center of rotation, and a location of the center of rotation of the connecting bores of the circular motion path is the same as the chainring center ; and a crankarm having a plurality of connecting arms at an end thereof, and an axial bore at the end having the connecting arms , wherein the crankarm has a center of rotation at a center of the axial bore , each of the connecting arms has a bore , and distances between centers of the bores and the center of rotation of the crankarm are the same; wherein the connecting arms of the crankarm are selected to be secured to the connecting bores of the first noncircular motion path or the connecting bores of the circular motion path of the chainring ; the chainring provides a first noncircular path of motion when the connecting arms of the crankarm are secured to the connecting bores of the first noncircular motion path, and the chainring provides a circular path of motion when the connecting arms of the crankarm are secured to the connecting bores of the circular motion path. <EOS>