Guide: How to Build a Fixed-Gear Bike – Frame, Hubs, Chainline, and Components

1. Fixed Gear or Singlespeed – what is the difference?

On a fixed gear, the rear sprocket is fixed to the hub. When the rear wheel spins, the chain, crankset, and pedals also move.

There is no freewheel.

Since the sprocket is fixed on a fixed gear, chainline, chain tension, sprocket, and lockring are more important than on a regular singlespeed.

2. Start with the right frame

Start with the frame. It determines which hubs, bottom brackets, tires, and, to some extent, cranksets you can actually use.

• Horizontal or rear-facing dropouts.
• The distance between the rear dropout ends, OLD.
• Bottom bracket standard and threading in the frame.
• Clearance for the tire width you want to use.
• Whether the frame has brake mounts.
• Pedal clearance from the ground.
• Toe overlap between the front wheel and your foot.

On a fixed gear, you tension the chain by moving the rear wheel forward or backward. That is why horizontal track ends work best.

Vertical dropouts, which are found on many modern road frames, make it significantly harder to achieve the correct chain tension and are therefore rarely a good starting point for a typical fixed-gear build.

If you are building on an older frame, you also need to check the threading in the bottom bracket shell. BSA/English (1.37" × 24 TPI) is the most common today, but older Italian frames may have ITA (36 × 24 TPI), and older French frames may use 35 × 1 mm.

The frame's country of origin can provide a clue, but do not assume that an Italian frame has an Italian thread or that a French frame has a French one. Check before ordering a bottom bracket.

A fixed gear does not have to be built on a dedicated velodrome frame either. If the bike is to be used in the city, clearance for wider tires, brakes, and a less extreme riding position can be much more useful.

3. Rear hub – 120 mm is most common, but 110 mm is available

The most common modern width for a track or fixed-gear rear hub is 120 mm OLD. Many track frames and fixed-gear frames are built for this.

But older Japanese keirin frames can be different. 110 mm is found on some older Keirin and NJS frames and hubs.

It is considerably less common today, but common enough to be worth checking if you are building on an older Japanese frame.

There are also other widths on converted road frames and some singlespeed bikes.

Measure the frame first – choose the hub afterward.

See our wheels, hubs, cogs, and lockrings.

4. Fixed-gear hubs, cogs, and lockrings

A genuine fixed-gear hub has two threads: one for the rear cog and one for the lockring.

The rear cog, or cog, screws onto the larger right-hand-threaded thread. A separate left-hand-threaded lockring sits outside the cog.

When you resist with the pedals, the cog is loaded in the opposite direction compared with when you pedal forward. The lockring prevents the cog from being able to unscrew from the hub.

Also check which lockring thread the hub has. Just because a lockring is left-hand threaded does not mean it fits all hubs. Common English/ISO is approximately 1.29" × 24 TPI LH, but Campagnolo, Phil Wood, Miche, and some other hubs may use different dimensions.

Never force on a lockring that does not run easily on the thread. Check the hub specifications if you are unsure.

See our track cogs, lockrings, hubs, and fixed-gear wheels.

5. Chainline – more important than almost anything else

The chainline is one of the most important things to get right on a fixed gear.

The front chainring and rear cog should be as straight behind one another as possible.

A poor chainline can cause:

• More noise.
• More friction.
• Faster wear on the chain, chainring, and cog.
• Uneven chain tension.
• Increased risk of the chain coming off.

Many classic track components are built around approximately 42 mm chainline, but that is not a measurement that applies to all hubs and cranksets.

The hub, crankset, bottom bracket, axle length, and which side of the spider arms the chainring is mounted on can affect the chainline.

Measure the chainline. Don’t assume it will be correct just because both the hub and crankset are marked “track”.

6. Crankset, bottom bracket, and crank length

The crankset and the bottom bracket together determine where the chainring sits and therefore which chainline you get.

With a square-taper crankset, it is not enough to choose the right axle length. You also need to know whether the crankset is made for JIS or ISO.

The two standards look almost identical, but the shape and dimensions of the square taper differ. If you mix the wrong crankset and bottom bracket, the crank arm may sit too far in or too far out on the axle. This can shift the chainline by several millimeters.

If you have an older frame, you also need to check the frame's threading itself. BSA/English is usually 1.37" × 24 TPI and 68 mm wide. ITA is 36 × 24 TPI and normally 70 mm. Older French frames may have 35 × 1 mm.

With square-taper cranks, three things therefore need to match: the threading in the frame, the correct axle length, and the correct square-taper standard.

Also check the crank arm length. 165 mm is common on the track and fixed gear because it provides a little more clearance between the pedal and the ground when pedaling through a corner.

170 or 172.5 mm works for many street builds, but it depends on the frame geometry, bottom bracket height, tires, and pedals.

See our bottom brackets for fixed gear, singlespeed, and other bikes.

7. Chainring, BCD, and 1/8" or 3/32"

When choosing a chainring, you primarily need to check the BCD and which chain width you intend to use.

BCD stands for Bolt Circle Diameter and specifies the bolt circle on the crankset. 144 BCD is very common on classic track cranksets, but other standards are also available.

Chainring, chain, and cog should be selected as a system. Do not mix different dimensions without first checking that the parts work together.

8. Choose the right gear ratio

The gear ratio is simply the number of teeth at the front divided by the number of teeth at the back.

• 48 × 16 = 3.00
• 48 × 17 = 2.82
• 48 × 18 = 2,67
• 46 × 17 = 2,71

A higher gear ratio gives you more speed per pedal revolution, but makes it harder when accelerating or riding uphill.

A lower gear ratio makes the bike easier to get moving and gives you a higher cadence. This is often more pleasant in dense city traffic.

A gear ratio that works perfectly on a velodrome therefore does not necessarily have to be particularly enjoyable in Stockholm traffic.

9. Skid Patches – worth knowing if you skid

When you skid, the rear wheel tends to lock up in the same places relative to the crank position. Those points on the tire are usually called skid patches.

How many skid patches you get depends on the combination of the number of teeth on the chainring and rear cog. If you can initiate a skid with both legs forward, the number of wear patches can also double for certain gear ratios.

It is not something you need to build the entire bike around, but if you skid a lot, it may be worth considering when choosing between, for example, a 16- and 17-tooth cog.

*The number may vary depending on whether you skid with only one or both legs forward. Therefore, 48 × 16 can result in 1 or 2 wear patches depending on your technique.

Changing from 16 to 17 teeth at the rear can therefore result in significantly more wear patches on the tire, while the change in gearing is fairly small.

10. The chain – do not tension it too tightly

On a fixed gear, the chain is under load both when you pedal and when you resist through the pedals. Therefore, both chain quality and correct chain tension are important.

The chain should have a little movement. It should not be extremely tight.

Excessive chain tension increases the load on:

• Hub bearing.
• Bottom bracket bearing.
• Chain.
• Cog.
• Chainring.

Rotate the crankset one full turn when checking the chain tension. Almost all drivetrains have a point where the chain becomes slightly tighter.

Set the chain tension at the tightest point.

When you pull the rear wheel back to tension the chain, you should also check that the rear wheel is still straight and centered in the frame.

We mainly use Japanese track chains from Izumi and D.I.D. You can find our fixed-gear and singlespeed chains here.

Want to learn more about chain widths and different track chains? We have a separate guide:

→ Guide: Choose the right bicycle chain for Fixed Gear & Singlespeed

11. Wheels and tires – choose them according to how the bike will be used

A fixed-gear wheel does not need to be tall, heavy, or extremely aero.

For a bike used in the city, it is often more important that the wheel is durable, easy to service, and built for the surfaces you actually ride on.

• Correct hub width.
• Number of spokes.
• Rim width.
• Hub bearings and serviceability.
• The cyclist’s weight.
• The roads you ride on.
• If the bicycle is to be used year-round.

On many city builds, 28–32 mm tires work very well. They provide more comfort and better grip than narrow track tires without making the bicycle feel sluggish.

But first check that the frame, fork and rim are all compatible with the tire width you plan to use.

See our wheels, hubs, rims and tires.

12. Handlebars and riding position – Drop, Riser, Flat or Bullhorn?

The handlebars make a big difference to how the bicycle feels and what it works best for.

Wide riser bars and MTB handlebars have also become common on fixed-gear bikes. The extra width provides a lot of control and leverage in heavy traffic.

Choose your handlebars based on how the bicycle will be used. An ultra-narrow track handlebar may look right on a velodrome bike but be rather impractical between buses and taxis.

See our handlebars, stems and grips.

13. Pedals, straps and clips

On a fixed gear, the pedals continue to rotate as long as the bicycle is moving. Therefore, it is important to have good control of your feet.

Common solutions include:

• SPD / clipless: Secure and works very well once you are used to the system.
• Pedal straps: Common on modern fixed-gear builds and work with regular shoes.
• Toe clips and straps: The classic solution for track and keirin bikes.

The important thing is to sit securely on the pedal while still being able to get out quickly when you stop.

See our pedals and accessories.

14. Brake or brakeless?

Brakeless is part of both track and messenger culture. But a velodrome and regular city traffic are two completely different environments.

On a fixed gear, you can brake and control your speed by resisting the pedals, but this does not provide the same braking force as a proper brake.

For road use, we recommend a front brake. During hard braking, the front wheel provides most of the braking force.

15. Final check before your first ride

Go over the bike once before you start riding it properly.

Simplicity is the whole point

A fixed-gear bike consists of few parts. That is also a big part of its charm.

But when gears, a cassette, freewheel, and shifters are removed, it becomes immediately apparent if the remaining parts do not work well together.

A good hub, a straight chainline, sensible gearing, and a correctly assembled drivetrain do more for the bike than an expensive name on the crankset.

A good fixed-gear bike should be quiet, responsive, simple, and fun to ride.

Build it for how you actually intend to use it.

Building a fixed-gear bike?

We build and work on fixed-gear and singlespeed bikes in our shop and workshop on Södermalm in Stockholm. Unsure which hub, crankset, bottom bracket, cog, or chain is right for your frame? Feel free to send us information about the frame and the parts you are considering, and we’ll help you figure out what works together.