Monocycles had been invented at long time ago for the benefit of running faster and easier. Bicycles were later invented for people may easily get balance on a bicycle than a monocycle. To drive a bicycle, chain plate and discs are two essential equipment. However, the original chain plate, as shown in FIGS. 8, 9, and 10, exists too much clearance for the purpose of switching gears and the clearance may cause noise, jams or disengagement.
The inventor, in view of this, has invented the present invention to improve the above-mentioned shortcomings