Gear shifters are an essential part of your transmission system enabling you to move up and down the range of gears to suit the demands of terrain, speed etc.
With derailleur gears, there are a number of different types but they all do the same job – pulling precise lengths of gear cable to move the derailleurs and change up or down gears. The front gear shifter will move the front derailleur to shift between chainrings (so will have either two or three gears, depending on the number of chainrings) and the rear shifter will operate the rear derailleur (typically 9-10 speed on most road and MTB bikes as per the number of sprockets in the rear cassette, with 7/8 speed on some city bikes or older MTBs and 11-speed on high-end road racers).
Indexed shifters vs. friction shifters
The vast majority of modern shifters (for road and MTB) are indexed, meaning that each ‘click’ of the gear shifter moves a precise length of gear cable, equivalent to one gear shift (assuming the gears are correctly adjusted). Older models used friction shifters, where the rider had to learn exactly how much to move the shift lever in order to change gear.
Road shifters vs. MTB shifters
There are a number of different types of shifter, depending on manufacturer and transmission system, but the biggest difference is between road and MTB shifters, or more accurately between shifters designed to be mounted on bikes with drop handlebars (‘racing’ bikes), and those designed for bikes with ‘normal’ handlebars. The former use a combined brake- and gear-shifter unit, part of which (the ‘hood’) is also intended as a hand rest while cycling while the latter are positioned under the handlebars just inside the grips, where they can be activated with thumb and forefinger.
NOTE: A properly-indexed gear system is a pleasure to use but requires regular maintenance and adjustment. One of the primary reasons for degradation in shifting performance is cable quality. Cheap cables will quickly stretch and/or corrode, affecting the adjustment of the gearing, while cable housings can also become clogged with mud and water. Use only good-quality cables, lubricate frequently and if you are regularly riding in poor conditions change your cables every once in a while or consider a set of fully sealed cables to keep out the elements.
When choosing a new set of road or MTB shifters (for upgrade or replacement) be sure to match them with your existing transmission – an 11-speed rear setup will need an 11-speed right shifter, etc. It is advisable not to try to mix and match transmission parts from different manufacturers as they may not be compatible. Different makers use varying standards in their systems (e.g. the amount of cable actuation, or the length of cable pulled per individual shift, varies according to manufacturer) so replace like with like.
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There are two main types of MTB derailleur shifter: trigger shifters and the less common twist shifters.
• Trigger shifters: Also known as ‘rapidfire’ shifters, these are located below the handlebar. Riders use a thumb button to shift to larger sprockets and a small index-finger operated ‘trigger’ to downshift.
NOTE: Shimano has also developed a combined brake/shifter aimed at the off-road market, but separate trigger shifters remain the most popular choice among riders of MTBs and other non-drop handlebar bikes, for ease of use and for the ability to use different gear and brake systems.
● Twist shifters: Twist grip shifters – similar to those used on motorbikes – have been developed for MTBs with the most popular being made by SRAM. They have their fans among commuters as well as racers looking to shed weight, but trigger shifters dominate.
The majority of drop-handlebar road bikes now feature combined brake lever and gear shifter units, with names and functions differing between the three main manufacturers (Shimano, Campagnolo and SRAM). Shimano call theirs STi (System Total Integration) while the Campagnolo standard is Ergopower and SRAM use what they call Doubletap.
The main characteristics of the three (mechanical) standards are:
• Shimano STi: Riders shift to larger sprockets by pressing the brake lever sideways, and downshift by pressing a small, separate lever just behind the brake lever (except with some lower-end groupsets, which uses a small lever on this inside of the brake hoods, pressed with the thumb).
• Campagnolo Ergopower: This uses a small lever behind the brake lever to upshift (rather than the brake lever itself), and a small button inside the hoods to downshift. The Ergo system is also indexed on the right side only (not for moving between chainrings, which is friction shift), while SRAM and Shimano systems are indexed on both sides. This makes Ergo shifters compatible with all chainring sizes, and double or triple chainsets, whereas Shimano/SRAM shifters must be specifically matched to the size and number of chainrings to be used.
• SRAM Doubletap: This uses a single lever to change up and down gears – you tap the lever in one direction, but by different amounts. Short, rapid taps move the gears up, while downshifting comes via a longer sweep of the lever.
Meanwhile the advent of electronic groupsets has meant that all three manufacturers are now offering electronic versions of their shifter units (Shimano Di2; Campagnolo EPS; SRAM Red). The shifter units in each case are nominally similar, but instead of pulling a precise length of cable (as with a mechanical system), moving the gear lever instead sends an electronic signal (either via cable or wirelessly, depending on the system) to the relevant derailleur telling it to shift up or down.
Finally, there are also specific types of shifter for TT bikes with aero bars, which are mounted on the bar ends.