The complete guide to bicycle gears — bicycle transmissions explained

A complete beginner's guide to gears, what you might find and how to use them

All too often you will see people spinning their pedals manically or laboriously grinding their way along, barely able to move the bike. We can’t help but feel life would be a little bit easier if they were using their gears properly, so we’ve put together a guide for those that need to learn how to use the gears on a bike.  


What are gears on a bike?

Gears are one of those lovely inventions that allow us to ride faster, get up hills more easily and get a lot more enjoyment out of our riding.

Gears convert the effort you put in at the pedals to a certain output at your wheel. There’s only so much force your muscles can produce and usually an optimum cadence (how fast you spin your pedals) at which you’ll be most efficient.

Changing your gears based on the terrain and conditions to stay broadly in that band lets you move forward more efficiently.

There are a few different systems that bikes use to change gears, though by far the most common is the external drivetrain.

Bicycle external drivetrains explained

An external drivetrain with a front and rear derailleur
Oli Woodman / Immediate Media

The majority of bikes on the market today have external drivetrains, which have been refined into simple, lightweight and efficient systems.

Gears are changed on the cassette (a set of sprockets on the rear wheel) by the rear derailleur. This shifts the chain up or down the cassette. As the derailleur moves to change gear it forces the chain against ramps or steps, moving it onto a bigger or smaller sprocket.

The bike may also have a front derailleur, which shifts the chain between chainrings attached to the cranks.

The gears at the front provide large jumps, which effectively change the range of your gears, so that they are more suited to high speed, flat terrain or low-speed climbing. The cassette allows you to select your gear more precisely within that range as you modulate your effort.

You will usually find between one and three chainrings (single, double or triple chainset) and up to 11 sprockets (12 exist too in the form of SRAM Eagle and Campagnolo Record) on the back wheel. That gives you a huge range of gears to choose from.

What is a hub gear on a bike? 

A Shimano Alfine 11-speed hub with Gates Carbon Drive belt
Jonny Ashelford

Hub gears are a popular option for commuters and those who want a robust and relatively maintenance-free drivetrain. With service intervals ranging between 3,000–5,000km, internal hub gears are great for the less maintenance-inclined.

There’s also no doubt that derailleurs are relatively exposed and susceptible to damage. Having everything nicely packaged away inside your rear wheel lets you breathe that little bit easier. During the winter having your gears protected from the elements doesn’t hurt either.

There’s lots of hub gears options available, but the most common are available from Shimano, SRAM, Sturmey Archer and the well-known manufacturer, Rohloff. With systems ranging from three to 14 gears there’s a wide range of options for whatever terrain you find yourself on.

However, the main drawback is weight. You’re riding around with a small gearbox inside your hub and that in turn contains a lot of metal parts that adds substantial heft.

Do bikes have a gearbox? What is a gearbox bike?