The chainring is an essential part of the bicycle. It is intended to be placed on the crankset. It must be chosen with great care. On the bike, there can be 1 or 2 or 3 chainrings. The chainring is a sprocket on which the chain links of the bicycle are placed. The diameter of the chainring attachments is an essential piece of information to know if a chainring is compatible with its crankset. This measurement is called BCD (Bolt Circle Diameter). The chainrings for vintage bikes are made of steel or aluminum.