Condensed answer: By default, a fixed-gear bike a.k.a. fixie isn’t designed for disc brakes. That said, it’s possible to add a front and rear disc brake, but the process will require the replacement of the fork, machining, and welding.
How Can One Add Disc Brakes to a Fixie
The simplest, the fastest, and to some extent the safest way to equip a fixie with a disc brake is to buy a fork with a disc brake mount.
The benefits of this approach are:
- By default, disc brake forks are strong enough to sustain the high torque created during braking via disc brakes.
- Replacing the fork on a bicycle is not the easiest task, but it’s not deeply complicated either. Most cyclists can do it successfully after educating themselves via YouTube videos.
- The front brake provides most of the stopping power.
During braking, there’s a weight shift to the front which increases the traction of the front wheel with the ground. As a result, the rider can apply more braking force through the front brake.
The downsides of this method are:
- Altered geometry
If the new fork doesn’t match the length and the offset of the old one, the geometry of the bicycle and subsequently the handling will be affected.
Hence why it’s important to find a fork with stats really close to those of the existing one – an often difficult task.
- Fewer Options For Retro Bikes
If your fixie is up to date, it will be equipped with a threadless headset and a basic 1 1/8″ fork.
Those forks come with a long steerer that the rider can cut according to their needs by using a hacksaw or a pipe cutter.
However, older fixies with threaded headsets and forks are limited when it comes to choices simply because there are fewer forks that answer the criteria. In the best-case scenario, you will find a threaded fork that has the length of the old one.
Technically, threaded forks can be cut too, but the process is more complex because they have to be re-threaded after the cut. Most people and even bikes shops do not have the tools for completing this procedure because the technology is considered old-school.
Unfortunately, this isn’t the only downside to threaded forks. Another problem is that most are designed for rim brakes and don’t have mounts for a disc brake.
- New style and color
Disc brake forks have a different style that may not complement the look of a traditional steel fixed-gear bike.
FAQ: Can I weld a disc brake mount onto the existing fork?
Standard rim brake forks are not tough enough to handle the torque of disc brakes. If you install a disc brake mount on such a fork, the disc leg of the fork may bend during braking.
Parts Needed for The Conversion (Front Only)
If you want to run a front disc brake on a fixie, you will need:
- A new fork
- Disc brake
- Brake cable and housing or a hydraulic system
- Brake lever compatible with the brake
- New front wheel with a disc brake ready hub
- Cable stoppers for the brake cable as most fixed-gear frames come without those
Adding a Disc Brake To The Rear of a Fixie
Adding a rear disc brake to a fixie is a highly problematic endeavor because:
- No Mounts
Standard fixed-gear frames do not have mounts for disc brakes. The only solution is to weld one. The procedure requires machining, welding, grinding, sanding and re-painting. If you don’t have the necessary tools, expertise, patience and time, it will be wiser to simply buy a new frame.
- Weak Chainstays and Seatstays
Disc brakes stress the frame. Therefore, frames that aren’t designed for disc brakes will most likely bend unless the rear triangle is reinforced with a brace. (An additional piece of metal welded to the chainstay and the seatstay on the disc brake side.)
It goes without saying that the procedure mentioned above will void the warranty of the frame.
- Narrow O.L.D.
The term O.L.D. stands for “over-locknut dimension” and refers to the usable part of a hub between the two locknuts.
The O.L.D. of a wheel should match the rear spacing of a frame. Otherwise, the wheel won’t fit.
Fixed-gear rear wheels have 120mm O.L.D. Meanwhile, rear road wheels with disc brakes have 135mm O.L.D.
Therefore, a rear road wheel won’t fit on a fixie unless the frame is cold-set (bent). Cold-setting can be done only on a steel frame and voids the warranty.
Thus, you will have to find a 700c fixed-gear wheel with a disc-brake ready hub – a rare part absent from most bike shops.
Alternatively, you can build the wheel yourself. You will need a fixed gear rear hub designed to take a disc brake (e.g., Novatec D566SBT 32) and new spokes.
- Inconvenient Installation of The Rear Wheel
Putting on the rear wheel on a fixed-gear bike and setting the correct chain tension is hard enough as it is. By adding a disc brake, one complicates the rear wheel installation process even more.
Fixed-gear bikes already have a rear brake (the pedals).
Parts Needed For The Conversion (rear only)
If you want to put a rear disc brake on a fixie, you will need:
- Disc brake mounts + frame reinforcement
- New rear wheel
- Brake caliper
- Cable and housing or a hydraulic system
- Brake lever
- Cable stoppers for the brake cable
The Benefits of Installing Disc Brakes On a Fixed Gear Bike
- Superior braking power
Disc brakes offer the highest braking power. They beat rim brakes in wet and even dry conditions.
- No need to replace rims often
Unlike rim brakes, disc brakes do not wear down the rim. Thus, the rim is no longer disposable.
Fixed-gear bikes with disc brakes are a rarity.
The Cons of Installing Disc Brakes On a Fixed-gear Bike
- Expensive and time-consuming
Putting disc brakes on a fixed-gear bike is not a straightforward process. A decent degree of frustration should be expected.
Also, you will have to spend a fair amount of money on labor and parts.
- Extra weight
Disc brakes are heavier than no-brakes or rim brakes.
- Different Aesthetics
Disc brakes will alter the aesthetic of the bike.
Standard Fixed-Gear Braking
At their core, fixed-gear bikes are track bikes. Track bikes are designed for reaching high speeds in a velodrome and do not have dedicated brakes.
The main reason for the absence of brakes on track bikes is to ensure a predictable braking pattern and thus minimize the chances of a collision.
If the bikes were equipped with brakes, it would be more difficult to predict how fast the competitors will slow down.
Fixed-gear bikes and track bikes don’t have a freewheel. If the bike’s moving so are the pedals. Consequently, the rider can brake by resisting the rotation of pedals and locking the rear wheel.
Classic track bikes do not have mounts for brakes, but many fixed-gear bikes come with drillings for rim brakes on the frame and fork.
Why Fixed-Gear Bikes Aren’t Designed For Disc Brakes By Default
The reasons why fixed-gear bikes do not use disc brakes by default are:
Disc brakes are considered a novelty in the road bike world and are yet to become the norm. Thus, the likelihood of seeing them as a default option on fixed-gear bikes which often don’t use even rim brakes is quite low.
- Not wanted by riders
One of fixed-gear bikes’ appeal is their simplicity. The people who are the most likely to ride a fixie appreciate the clean look of the bike and don’t find disc brakes aesthetic and complementary to the rest of the components.
Disc brakes are heavier than rim brakes.
Also, disc brakes require a reinforced rear triangle and fork because standard rim brake frames and forks are not designed to deal with the stress created by disc brakes. The extra material results in extra weight.