| 摘要 |
A bicycle derailleur gear shifting system having a rotatable handgrip actuator cam (74) which is coupled with derailleur shifting mechanism (54) through a control cable system (60, 64) so as to control the derailleur mechanism (56, 58). Separate actuator cams are associated with the front and rear derailleurs. For the down-shifting direction, at least the rear derailleur cam is configured so as to substantially compensate for increasing force of the derailleur return spring (208) so as to substantially compensate for numerous cumulative lost motions in the derailleur shifting mechanism (54) and cable system (60, 64), and for chain gap variations; and so as to overshift the chain a sufficient amount beyond the destination freewheel sprocket (54a) so that the chain will approach the destination sprocket (#5) in the same direction as it would in the up-shift direction, but not sufficient to cause a double shift, or derailling from the #1 sprocket. A front derailleur cam is configured to provide fine-tuning for ''cross-over'' riding. |
