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:

  • ​front chainrings (a.k.a crankset)
  • rear cassette
  • chain
  • derailleurs
  • shifters   

 
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

 MOUNTAIN BIKES

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.

Copyright © Foresttrek Cycle Centre. All rights reserved.

Derailleur Gears: A practical guide to their use and operation

  • Gears. Amazing things. The combination of two different sized cogs and a chain lets you power down hills, cruise on the flat and climb up a gradient. What a great invention. Not that I'm knocking single speeds - which we all ride here in the workshop - but the multi-geared bicycle is a formidable invention.

    ​Changing gears, though, is another matter. Most modern bikes are equipped with a derailleur gearing system - stay with me, we’ll get to the terminology - where the chain runs between many different cogs. These cogs are both turning between your feet and attached to the rear wheel, giving the rider a sometimes bewildering number of gears to choose between, the most common being 21, 24 or 27.

    ​When riding a bike, your body can only produce so much power before you run out of energy. Gears on a bike help you ride more efficiently and consistently so you can sustain your energy longer. Understanding how your bike gears work can help you choose the right components when you’re bike shopping. It will also help you get the most enjoyment out of your bike when you’re out on a ride.