The chainring is an essential part of a bicycle. It is designed to be placed on the crankset. It must be chosen with the greatest care. Your bike may have 1, 2 or 3 chainrings. The chainring is a toothed wheel on which the links of the bicycle chain are placed. The diameter of the chainring attachments is a vital piece of information to know if a chainring is compatible with its crankset. This measurement is called BCD (Bolt Circle Diameter). Chainrings for vintage bikes are made of steel or aluminium.