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A bicycle shifter or gear control or gear levers is a component used to control the gearing mechanisms and select the desired gear ratio. Typically, they operate either a derailleur mechanism or an internal hub gear mechanism. In either case, the control is operated by moving a cable that connects the shifter to the gear mechanism. Shifters are mounted on the down tube of the frame, stem, or various locations on the handlebars. Manufacturers of shifters include Shimano, Campagnolo, Microshift, Sturmey Archer, and SRAM. Shifter controls are mounted so that the right shifter controls the rear derailleur and the left shifter controls the front derailleur. For hub gears, the control is also mounted on the right. Various shifters designs have included friction shifters and index shifters, which do not require fine-tuning during a gear change, as well as shifters integrated with the brake controls. ==Friction shifting== Originally, gear control levers consisted of a simple lever. Changing gears required pushing or pulling the lever so that the derailleur would move the chain to a different sprocket on the rear hub. The cyclist would need to adjust the lever to center the chain on the sprocket. This system started out with 2 or 3 sprockets, and by the 1970s had developed to 5 and 6 sprockets. Many inexperienced cyclists, especially those who started in the US 1970s bike boom, found it difficult to change gear accurately. Typical difficulties included gear changes that left the chain in between two sprockets, which causes noisy rattles, or undesired and unexpected gear changes. However, many experienced cyclists still prefer friction gears for their simplicity and long-term reliability, as well as the ability to mix and match components from different manufacturers without the compatibility issues of indexing systems. Another benefit of friction shifting is the ability to shift from the lowest to highest gear in one simple motion. In addition, the introduction of ramped freewheel sprockets (such as Shimano's Hyperglide system) and derailleurs with floating jockey wheels has made accurate gear changes much easier than previously. Friction or ratcheting shifters remain popular for front derailleurs, since only two or three chainrings are used, and allow trimming of the front derailleur. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Shifter (bicycle part)」の詳細全文を読む スポンサード リンク
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