What Is the Difference Between a Single Speed and a Fixed Gear (Fixie) Bike?

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A single speed and a fixed gear bike will look very similar to most people when you put them side by side, but what is the difference between them? The main difference between a single speed bike and a fixed gear bike is that you can coast on a single speed. On a fixed gear, you are pedalling, or you are stopped. If you want to know more then, please read on.

A single speed bike will use a similar hub to a geared bikes hub, in some cases precisely the same hub but with only one cog and some spacers instead of a cassette or a single speed freewheel. To allow you to coast these hubs, use freehubs and freewheels with a ratchet and pawl system.

A freewheel is the original way that bikes ran gears. The freewheel was a cassette with the ratchet and pawl system built-in, and this section screwed onto your hub. A freehub is the ratchet and pawl part of the freewheel built into your hub, and a cassette can then slide onto it.

A Halo freewheel hub, notice the threaded section
A Halo cassette hub, notice the freehub section sticking out from the hub.
Freehub removed from hub, you can easily see the pawls
The inside of a single speed Halo freewheel
A Sunrace cassette showing how it splines it uses to slide onto the freehub body

How does a ratchet and pawl system work?

A ratchet and pawl system

When you put your foot down to pedal, the pawls inside your freewheel engages against the ratchets. As you pedal, the pawls stay engaged in the ratchets. If you slow down or stop pedalling, the pawls disengage. You can then hear a clicking which is the pawls now running across the top of the ratchet mechanism but not catching.

The pawls not engaging is what allows you to coast. The ability to coast is also why you’ll need front and rear brakes on a single speed bike.

How does a fixed gear work then?

The clue is in the name. Fixed. Your cog is fixed to the hub body.

A Halo track hub, notice the threaded ends again
A Halo track cog, notice there is ratchet and pawl mechanism

As you can see from the hub and cog, there is no ratchet and pawl mechanism. By not having a mechanism like that, the cog is then a mechanical extension of the hub, and once you put a chain on, it has become coupled with the pedals. There is no way for the hub to move if the pedals aren’t moving and vice versa.

As your pedalling speed is now what sets the bikes speed, you don’t need a back brake. Legally you’ll need a front if you want to ride on roads. You can also still run both brakes if you feel it will keep you and others safe. It takes a little time to learn to ride brakeless, so don’t ditch your brakes until you can stop quickly and safely.

Is fixed gear better than single speed?

People have spent years arguing whether single speeds are better than fixed gear and vice versa. The answer, as with many things, is subjective. The ultimate arbiter is you. You’ll prefer a fixed gear, or you’ll prefer a single speed. You might even prefer a single speed for certain rides and fixed gear for other kinds of riding. Just go with your heart, and you’ll have made the right choice.

Just remember and stay away from gears, those are evil.

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