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15. Shifters #18 . Top
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In the 1970's on till about 1990, the gear shift mechanism on all derailleur bikes were little levers mounted on the down tube. There were two levers, one for the front chain rings and one for the rear freewheel. The shift cables ran down the outside of the tube to the deraileurs. To shift gears you just reached down and moved the lever quickly forward or back and the gears would shift. This was the simplest system ever developed: short cables and totally independent of how many gears.
Then in the 1980's or so, some bikes put the shifters on the end of the handlebars. These are called Bar End shifters. The original bar end shifters were also just friction.
In the 1990's Shimano developed indexed shifting. They standardized the spacing of the chain rings and cogs, and then built shifters that clicked the cable just the right distance from gear to gear. This system was called "Indexed" shifting.
BarType Indexed Combined
Trigger Flat Indexed no
Thumb Flat Both no
Twist Flat Indexed no
Combo Flat Indexed Yes
BarEnd Drop Both no
Downtube Drop Friction no
STI Drop Indexed Yes
FLAT BAR SHIFTERS
- Trigger Shifters
The definition of a trigger, as opposed to a thumb shifter is that there is an actual spring release into each gear. And they can't be put into friction mode.
- Thumb Shifter
These can be either in friction mode or indexed.
The original flat bar shifters in the 1980's could operate in either friction mode, or indexed mode. I have always run mine in friction mode because it's simpler. They still sell this type of flat bar friction shifter, but they are rarely put on mainstream bikes.
Combined brake lever and shifter for flat bars. Eg: Shimano Altus ST-EF500
DROP BAR SHIFTERS
- Downtube shifters
Downtube shifters are still the simplest and most flexible system. The adjustment is simple: just two "stop screws" on the deraileur, to prevent the chain from coming off at either end. It is up to the rider to move the lever an appropriate amount to shift the gears. Once you are used to them, you just flip the lever forward or back a littleand you get the next gear. If you really want to shift quickly several gears, you pull the lever a bigger amount. Downtube shifters work perfectly well with the latest cassettes. And if you want to change to a cassette with more or less cogs, it is no problem because the shifter has no notion of how many cogs there are.
- Bar End shifters
Bar end shifters are still common on touring bikes with drop handlebars. They stick out of the ends of the handlebars, and the cables run under the bar tape to the bend in the bars and then go back to the deraileurs. They can be used in either friction or indexed mode.
- Integ STI
The most common type of shifter these days on drop bar bikes uses a combined brake lever and shift mechanism. Typically you flip the lever sideways to shift gears, whereas the brakes you pull in. Shimano calls this "STI" shifters (Shimano Total Integration)
For all types of shifter, the grip area diameter of the bars is seldom listed, because all normal drop bars are 23.8mm and all normal flat bars are 22.2 mm.