What Is a Single Speed Bike? | One Gear, Zero Shifting

A single speed bike has one gear ratio and no shifting system, letting you coast thanks to a freewheel hub.

If you’ve ever ridden a bike with no gears, you already know the basics of what a single speed bike is. These bicycles strip cycling down to its essentials: one front chainring, one rear cog, and a chain connecting them. There are no derailleurs, no shifters, and no cables. You pick one gear, and that’s what you ride for the entire trip.

The appeal is simplicity. Fewer parts mean less to maintain, less to break, and less weight. That’s why single speeds show up everywhere from BMX tracks to city commutes. But there’s a common confusion worth clearing up right away: a single speed bike is not the same thing as a fixed-gear bike, and it’s not “gearless” either.

The Core Definition: One Ratio, No Shifting

A single speed bike is defined by its drivetrain having exactly one gear ratio. The bike has a single chainring at the pedals and a single cog at the rear wheel, and there’s no mechanism to move the chain between different sizes of gears. The rider cannot change gears while riding, per the standard definition on Wikipedia’s single-speed bicycle entry.

That doesn’t mean the bike has no gears at all. It still has a gear ratio — the relationship between the size of the front chainring and the rear cog. It just has only one of them. Calling a single speed “gearless” is a common mistake; the bike has a gear, just a single fixed choice of one.

Single Speed vs. Fixed Gear: The Coasting Difference

This is the distinction that trips up most people. Single speed bikes and fixed-gear bikes both have one gear ratio, but they behave differently when you stop pedaling.

Single speed bikes typically use a freewheel hub. A freewheel lets the rear wheel keep turning while the pedals stay still, which means you can coast. When you stop pedaling on a single speed, the bike rolls and your feet rest comfortably on the pedals.

Fixed-gear bikes — often called fixies — don’t have a freewheel. The rear cog is bolted directly to the hub, so the drivetrain is always linked. If the wheel turns, the pedals turn. You cannot coast on a fixed-gear bike; your legs keep moving as long as the bike is rolling. This is the defining mechanical difference, and it’s why the two terms should never be used interchangeably.

What Are Single Speed Bikes Used For?

Because they’re simple, durable, and light, single speed configurations appear across many cycling disciplines. Wikipedia’s overview lists BMX bikes, track bikes, fixed-road bikes, mountain bikes, jump bikes, and many children’s bikes as common single-speed applications.

Here’s the practical breakdown of where you’ll see them:

• BMX and jump bikes: Riders need immediate, predictable power with no derailleur to damage on landings.
• City commuting: Flat urban routes don’t need multiple gears, and fewer parts mean less maintenance.
• Children’s bikes: Kids learn to balance and pedal without the distraction or complexity of shifting.
• Track and velodrome racing: These typically use fixed gear setups for maximum efficiency.

The trade-off is terrain. With only one ratio, you pedal the same cadence on flats and hills alike, which makes steep climbs and fast descents less forgiving. The British cycling advocacy group Cycling UK’s guide to riding single speed bikes notes that riders must adapt their approach to hills since there’s no easier gear to shift into.

Converting a Geared Bike: Not a Simple Swap

If you’re tempted to convert an old geared bike into a single speed, understand that it’s a drivetrain project, not a quick adjustment. A geared bike’s frame typically has horizontal dropouts or derailleur hangers designed for indexed shifting, and simply removing the derailleur won’t work because the chain needs the right tension.

Running one chainring and one rear cog usually requires a chain tensioner, a new hub, or a frame with sliding dropouts. The bike also needs a chainline that runs straight from the front ring to the rear cog. For many riders, buying a purpose-built single speed bike is the more practical route than rebuilding a geared one.

If you’re ready to buy, our roundup of the best 1 speed bikes on the market breaks down the top options and what each one does best.