Understanding the Bike Drivetrain
There are five main parts of the standard bicycle that let you shift gears and change how easy it is to pedal your bike. They are comprised of the following:
The crankset, rear cassette, chain and derailleurs are known collectively as the drivetrain, pictured here:
Chainrings: Bikes have one, two or three front chainrings, also known as the crankset. A bike with two chainrings is called a double. A bike with three chainrings is called a triple. Each chainring has a number of teeth on it where the chain connects.
Cassette: Your bike’s rear cassette is the stack of cogs (gears) mounted on the right-hand side of your rear wheel, with the small cog farthest from the wheel and the large cog closest to the wheel. Each cog has a number of teeth on it where the chain connects.
Chain: The chain connects to the teeth on your front chainrings and the cogs on your rear cassette so that when you pedal, the chainrings and cogs turn the wheels and the bike moves forward.
Derailleurs move the chain between the front chainrings or between the rear cogs. Cables run from your shifters to your derailleurs. When you press on your shifter, it moves your front or rear derailleur so the chain moves where you want it to go.
Many bikes have front and rear derailleurs. Some mountain bikes have only a rear derailleur and therefore come with only one shifter. (These bikes have more cogs in the rear cassette, giving you a broad range of gear choices even with a single front chainring.)
Shifters let you move the chain between your front chainrings and the cogs of your bike’s rear cassette. Each shifter controls one cable attached to one derailleur.
On road bikes, the shifters are mounted either on the handlebar or they’re integrated with the brake levers. In older road bikes, they’re on the downtube or on the ends of your drop bars. On mountain bikes, the shifters are mounted on the handlebar
Bicycle Gears and Shifting Basics
Derailleur Gears: A practical guide to their use and operation
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Proper Shifting Technique
Shift the chain between the rear cassette cogs for small changes and between the front chainrings for big changes, but not both at the same time. Only use one shifter at a time, or you may mis-shift, jam the chain or drop the chain off the chainrings or cassette.
Try to anticipate the terrain, and shift right before you start climbing, not halfway up when you’re nearly stopped with maximum pressure on the pedals.
On flats, it’s okay to shift through several gears at a time. If you do shift on a hill, shift one gear at a time, and try to momentarily release pressure from the pedals as you’re shifting.
When you shift, don’t pick a gear that will put your chain on opposite extremes of the front cogs and rear cassette at the same time. Called cross chaining, this is where you’re most likely to drop or break your chain. Those same gears can be achieved with different combinations of chainrings and cogs.