Electronically servo-assisted bicycle gearshift and related method

The electric servo and method for the invention relates to the electric servo electric bicycle change mechanism, comprising the following steps: a) driving (207,211) bicycle change mechanism device at least comprises two chain gears' speed changing mechanism cluster's axial direction of the first direction or and first direction opposite second transverse chain; b) accepting position between the chain and speed-changing gear set predetermined chain gear succeeds to calibrate (205,305); informationc) is further b) chain wheel and a speed of related logic 11) are corresponding relation of (speed ratio and method and device of related). The invention also relates to suit part and method for bicycle change mechanism, and a to match this method for manufacturing process and circuit device.