Shoulders ( Shifters ) - in modern bicycles special devices that are attached to the steering wheel (previously attached to the frame) and allow you to change gears. The gear changes are carried out, as a rule, by transferring the force from the shafts through a cable drive to switches that change the position of the circuit on the stars in order to change the gear ratio . If the bike is equipped with two gearshifts (front and rear), the steering wheel is equipped with two shifters, and, as a rule, the shifter mounted under the left hand “answers” for the forward switch, and installed under the right arm - for the rear one. The shifters can also activate the gearshift mechanism integrated into the rear hub of the bike.
There is also the Acros A-GE system, in which one steering wheel controls both the front and rear switches using a hydraulic drive.
Initially, the shafts were of a frictional nature, and the cable, stretched to the necessary extent, ensuring the transfer of the chain to the desired star, had to be fixed with a nut or some other method. Serious progress in this area was achieved with the invention of the index method of gear shifting, when a ratchet mechanism was incorporated into the shifter .
By design, you can distinguish three main types of shafts - trigger (where switching is carried out by pressing the levers), “gripshift” ( eng. GripShift ), where switching is carried out by turning the handle around the steering wheel, and so on. “Dual-Control” ( English Dual-Control ) - here the cyclist switches gears by turning the brake handles in a plane perpendicular to the plane of their (handles) stroke for performing braking.
The shifters are also divided according to the number of gears, between which they provide switching.
Shifters are an integral component of bicycles that have more than one gear, in particular, mountain , road (where they are usually combined with brake handles and are often called "pistols", being historically the first example of dual-control shafts), cyclocross , pleasure, etc.
The most important manufacturers of shafts are Shimano , Campagnolo and SRAM .