How a Mountain Bike Gear Lever Works

Written by carl miller
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How a Mountain Bike Gear Lever Works
(Image 1: rbrwr:; Image 2: ragnar1984:; Image 3: D'Arcy Norman:

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Mountain bike gear levers, or shifters, usually come in one of four designs: twist, bottom-mounted, top-mounted, and integrated. However, they all perform the same basic function.

Clicking the gear lever, or knob (or whatever form it takes on your bike), either tightens or loosens the wire that runs from it to the gears. This adjustment in wire tension activates a mechanism called a derailleur. The derailleur basically derails the bike chain and places it on a different gear.

Mountain bike gear levers come in pairs--one on the left handle, one on the right. The lever on the left handle (looking at the handles as you would while riding) is usually numbered 1, 2 and 3 (1 and 2 only, on the older 10-speed bikes). The lever on the right varies in numbering, depending on how many gears the bike has--1 through 6 for 18-speed bikes, 1 through 7 for 21-speed, and so on.

Changing Gears

Clicking either lever up a number is called upshifting. When you upshift, the bike becomes harder to pedal, but moves farther, per pedal rotation, allowing you to go faster on downhill and level terrain. Clicking either lever down a number is called downshifting. When you downshift, the bike becomes easier to pedal, but moves less, per pedal rotation.

The lever on the left handle controls the derailleur on the front set of gears, called chain rings. In third gear, the chain sits on the largest chain ring--in first, the smallest. Switching between these three gears causes a large amount of change in tension.

How a Mountain Bike Gear Lever Works
Chainrings and front derailleur

The lever on the right handle controls the derailleur on the rear gears, or "cogs." The cogs work in reverse order, compared to the chain rings; upshifting moves the chain to a smaller cog and downshifting moves it to a larger one. However, upshifting and downshifting on the right lever still increases and decreases the tension, respectively. When you adjust the right-hand lever, smaller, fine-tune changes occur in tension.

How a Mountain Bike Gear Lever Works
Cogs and rear derailleur

Both levers work together to provide you with a full range of gear settings. With the left-hand lever in third gear, you can adjust the right-hand lever to switch between the highest settings. For example, on a 21-speed bike you experience the most possible amount of tension when in third gear on the left lever and seventh gear on the right. With the left-hand lever in first gear, you can use the right-hand lever to explore the lowest settings. You experience the least possible amount of tension when in first gear on both levers. In second gear on the left-hand lever you can adjust the right-hand lever to experience anywhere from moderately high to moderately low tension.

Keep in Mind

When the left-side shifter is in third gear, use only the highest few gears on the right side; when it is in first, use only the lowest few gears on the right; and when in second gear on the left, use all but the extreme numbers (on a 21-speed, first and seventh) on the right lever. This is because the chain can come loose or wear down the gears when running diagonally from a chain ring on the extreme left to a cog on the extreme right, and vice versa.

When changing gears, never pedal at full-speed; this can also cause problems between the chain and gears. You must pedal in order to fully change gears, but you should do so lightly.

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