Shifter (bicycle Part) - Shifter Designs

Shifter Designs

Older road bike shifters may be down tube gear levers, mounted on the down tube of the frame. These have been available both non-indexed (friction) and indexed. If the levers are not mounted on the handlebar, the rider would have to move a hand from the handlebars to the gear lever to change gears. This made changing gears difficult while turning, going up hill, maneuvering in traffic, or during a race, as the rider would lose some stability from having only one hand on the handle bar, while adjusting the lever. Friction shifters have the added disadvantage of having to be trimmed every time the gear was changed, which might take a few moments. This led riders to usually stay in one gear, unless they were about to rapidly change their speed. Indexed shifters addressed the trimming issue, but the stability issue remained.

Thumb shifters are simple shifters which used to be common on mountain bikes, essentially being a downtube shifter mounted on top of the handlebars. Stem-mounted shifters are also similar. These gave way to twist-grip shifters as developed by SRAM, which remain common on flat handlebars. 'Rapidfire' or trigger shifters use two triggers below the handlebar, one to change up and another to change down.