Adding a Transmission To a Fixed-gear Bike – Madness or Simply Genius?

It’s possible to add gears to a fixie, but the conversion is expensive and time-consuming. Often, it’s better to sell the bike and purchase one that’s already designed to operate with gears.

The Issues That You Will Face

1. No Derailleur Hanger

Fixed-gear frames don’t have a derailleur hanger nor dedicated mounts for it.

To install one, you will have to follow alternatives paths. The options are:

  • Chain Tug + Derailleur Hanger
Chain tug + Derailleur Hanger

The main function of a chain tug is to facilitate chain tensioning which could be a difficult task on a fixed-gear bike.

Some chain tug models come with a derailleur hanger that allows the installation of a rear derailleur too.

  • Weld a Derailleur Hanger

If the frame is made of steel, you can pay a frame builder to machine and weld a derailleur hanger to the drive-side chainstay.

If you have welding skills, you can cut the derailleur hanger of an old steel frame and weld it to the fixed-gear frame yourself.

If the frame is made of aluminum, this option is less desirable because aluminum is more difficult to weld and requires heat treatment which can be damaging to the frame.

  • A Derailleur Hanger Adapter For Rear-facing Dropouts

Another option is to install a derailleur hanger adapter for rear-facing dropouts.

The adapter comes with a derailleur hanger and slides into the dropouts. The axle secures it.

  • A Derailleur With Its Own Hanger

Some entry-level derailleurs (e.g., Shimano Tourney TZ500) come with their own hanger.

The downfall of this approach is that the derailleur will be a bit more finicky to install and will lose its position every time you remove the rear wheel.

2. 120mm O.L.D.

In most cases, the rear wheel on fixies has an O.L.D. of 120mm.

O.L.D. stands for Over Locknut Dimension and refers to the distance between the outer sides of the two locknuts found on the rear hub.


Meanwhile, the standard rear-wheel O.L.D. of modern road bikes is 130mm.

This means that you won’t be able to fit a contemporary road wheel at the back of a fixie.

This leaves us with the following options:

A. Rebuild Your Wheel Around a 120mm Geared Hub

Up until the 80s, road bikes had 5 gears and a rear hub with an O.L.D. of approximately 120mm. If you can find such a wheel, you can install it on the bike.

You can also search for a retro 120mm hub and build a wheel around it. You will be able to reuse your existing rim, but you will have to replace the spokes as they will be the wrong length for the new hub.

If you want a more up-to-date 120mm hub, look for SunXCD’s 120mm model. It’s a stylish, high-quality 120mm hub with a cassette driver. Unfortunately, it has sold out on most websites that I checked.

B. Cold Set The Frame To a Larger O.L.D.

Another option is to cold-set/spread the dropouts so that the frame can accept wider hubs.

Cold-setting is an option only when the frame is made of steel because steel is elastic and can withstand some degree of bending without losing its tensile strength.

In different, cold-setting an aluminum frame is bad practice and weakens the frame because the material is brittle.

After cold-setting the frame, you will have to realign the dropouts as they will no longer be parallel to one another. To do that, you will need a dropout alignment tool.

Note: This procedure will void whatever warranty your frame has regardless of its material.

3. No Cable Routing

Fixed-gear bikes don’t have gear cable routing because they aren’t designed for derailleurs.

This leaves the user with three options:

  • Run a gear cable from the shifter to the derailleur and zip-tie it to the frame. (This solution works but isn’t aesthetic.)
  • Install clamp-on cable stoppers on the top tube and run the cable through them.

The benefit of this approach is that you won’t have to deal with zip ties. However, some people may not like it because it isn’t as neat as possible.

  • Weld cable stoppers to the frame

This is the best method looks wise but also the most difficult to pull off.

First, you need to machine the cable stoppers, scrub off the frame’s paint at the attachment points and weld them to the top tube. Then, you have to repaint the frame.

Technically, you can re-paint only the top tube. But unless you can replicate the stock color, you will be left with spots of a different nuance. The only way to avoid this result is to repaint the entire frame in a new color.

4. Wide Chain

The chain of single-speed bikes is too wide for a cassette or a freewheel with multiple cogs. If you want to run gears, you will have to replace the stock one with a narrower model. Ideally, the chain should correspond to the number of gears at the back.

Note: You will need a new front chainring too because fixed-gear chainrings are too wide for narrower chains.

FAQ: Can I install a front derailleur on a fixie?

Technically, you could, but the set-up will become even more complicated, and you may have some chain line issues. Also, the cable routing will get even trickier.

It’s best to keep it simple and run a 1x drivetrain, at least at first.

FAQ: Can I install a front derailleur and run fixed-gear at the back?

Short answer, no.

If you install a front derailleur, you will also need a chain tensioner at the back. Otherwise, the chain will keep falling.

However, fixed-gear bikes place too much stress on the lower part of the chain when the cyclist resists the pedals or backpedals. The extra tension would break a rear derailleur or a dedicated chain tensioner.

If you want to run a solo front derailleur, you will have to convert the bike to a single-speed machine with a freewheel.

An Internal Gear Hub

Another solution is to install a 120mm internal gear hub.

The pros of this approach are:

  • You won’t have to mess with a derailleur hanger.
  • The simple look of the bicycle will be preserved because the gears will be hidden in the hub.
  • You will be able to change gears even when you’re not pedaling.
  • The gearing will be protected from the elements.

The cons are:

  • Since the O.L.D. of the bike is 120mm, your options will be limited. Most internal gear hubs in that range offer 2-3 speeds.
  • Internal gear hubs are not light. Most models 2-3-speed models weigh 950-1450 grams.
  • The complexity of internal gear hubs makes them difficult to service

The Parts That You Will Need

Below is a list of the parts needed for the conversion:

Option 1: Derailleur + Freewheel or Cassette

  • New hub + spokes or an entirely new rear wheel
  • A cassette or a freewheel depending on the hub
  • A rear derailleur
  • A rear shifter
  • A derailleur hanger
  • New chain
  • New chainring
  • Shifter
  • Cable + housing

Option 2: Internal Gear Hub

  • A geared hub + new spokes
  • Cable + housing
  • Shifter
  • New chain
  • New chainring

The Advantages Of Converting a Fixie To a Geared Bike

1. More versatility

Extra gears will allow you to cover more diverse terrain. The bike may transform from a casual machine into a full-time commuter.

2. Less stress on the joints

Fixed-gear bikes are known for placing extra stress on the knees because you’re always in the wrong gear (either too low or too high).

The extra gears will allow you to ride at a higher cadence and will subsequently reduce the impact on the joints.

3. You get to keep your frame.

If you really like the frame of your bike but can’t handle the punishment of fixed-gear or single-speed riding, a conversion to a geared bike can be a logical choice.

The Disadvantages of the Conversion

1. Expensive

The conversion won’t be cheap. You will have to spend a decent amount of money and time to make it work.

And if you have to pay for all the labor, you may be better off selling your existing bike and investing the money into a new one with gears.

2. Disrupted Lines

One of fixies’ strongest points is that they look clean. Once you add gears, the bike will lose some of its previous aesthetics.

Summary: What You Need To Know

1. You can convert a fixed-gear bike to a geared machine. There are two methods – derailleur + cassette/freewheel or an internal gear hub.

2. If you go the derailleur route, you will have to buy more parts, but the bicycle will be lighter and with a greater range.

If you go for an internal gear hub, the bike will keep its simple lines, but its weight will increase.

3. Unless the frame is very important to you, you can consider selling your current bike and buying a new geared one to save time, energy, and potentially money too.

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