Condensed Answer: V-brakes can be converted to disc brakes only when the frame and/or fork have disc mounts. If the frame or fork don’t have mounts, the user will have to compromise and choose a less than ideal option.
Requirements To Convert V-brakes To Disc Brakes
- Disc Brake Mounts
The number one requirement for converting V-brakes to disc brakes is the presence of disc brake mounts on the frame and fork.
There are three main types of disc brake mounts:
- International Standard
- Post Mount
- Flat Mount.
International Standard (IS) – in this case, the brake is secured to the fork’s leg via bolts perpendicular to the mount. This is an old-school standard absent on newer frames and forks.
Post Mount (PS) – post mount is the current standard. In this case, the brake is secured to the bike via bolts going towards the fork’s legs.
Flat Mount – as the name suggests, flat mounts are flush with the frame or fork. Currently, flat mounts are found only on road bikes and are limited to 160mm rotors.
FAQ: My bike has no disc brake mounts. Any options?
Option 1: Get a New Fork
One of the cheapest and most effective ways to add a disc brake to a “V-brake bike” is to get a disc brake-ready fork.
By doing so, you will be able to install a front disc brake and get most of the benefits that disc brakes have to offer.
The largest percentage of stopping power comes from the front brake. Hence the saying: “Front brakes are for stopping; rear brakes are for slowing down.”
The reason why the front brake is more effective is the additional friction that the front wheel has.
During braking, there’s a weight shift towards the front of the bike. As a result, the unweighted rear end loses traction with the ground and slides during aggressive braking.
What fork should I go for?
Ideally, the new fork will have the same parameters as the old one. This will ensure its compatibility with the frame and eliminate changes to the bike’s geometry.
The important properties are:
- Steerer Tube Thickness and Shape
The steerer is a tube passing through the head tube. The diameter of the steerer and that of the head tube should be compatible. If the steerer is too narrow, the headset bearings will be loose; if the steerer is too thick it won’t fit in the head tube.
The shape of the steerer near the crown should be compatible with the head tube too. There are two types – tapered (the lower part of the steerer is shaped like a cone) and non-tapered (the steerer is the same thickness from top to bottom).
It’s possible to use a non-tapered fork on a tapered frame, but the procedure will require additional adapters. It’s also possible to install a tapered fork on a non-tapered frame by relying on a lower cup with an external bearing. If you decide to do that, the fork will sit lower and will steepen the head tube angle of the bike.
In both cases, it’s more convenient to get a fork with a steerer designed to fit right from the start.
- Steerer Tube Type
There are two main types of steerers – threaded and non-threaded. Threaded forks use quills stems and are found on old-school bikes whereas non-threaded ones are the norm for the current production.
The new steerer should match the type of the old one.
- Steerer Length
The length of the steerer is also very important. If it’s too short, it may be impossible to install it securely. Also, a shorter steerer will lower the height of the handlebars and alter the rider’s position.
The steerers of non-threaded forks come longer than necessary. A mechanic or the user is expected to cut the steerer as much as needed for a proper bike fit. Consequently, there’s always a possibility for shortage when moving the fork from one bike to another.
Ideally, both steerers will be close in length. It’s also possible to successfully install a fork with a longer steerer, but in that case, the bike fit will change.
- Axle to Crown Length
Axle to Crown (ATC) is the distance between the fork’s dropouts and the fork’s crown. The ATC is dependent on the wheel size that the fork is designed for. It’s best if the new fork has close to the same axle to crown length as the V-brake one. Otherwise, the geometry of the bike will change.
FAQ: Can I switch from a suspension fork to a rigid one or vice versa?
In most cases, a switch from a rigid to a suspension fork is not worth it. If the bike isn’t originally designed for a suspension fork, its geometry will be altered significantly. Consequently, the handling of the bike will be weird. Additionally, the head tube will experience significant stress.
However, switching from a suspension fork to a rigid one can be done without altering the bike’s geometry. To do that, the user will need a suspension-corrected fork.
Suspension-corrected forks are longer rigid forks mimicking the angles of a non-compressed suspension fork.
Option 2: Get a New Frame
Another possibility is to replace the entire frame with one that has mounts for a rear disc brake. The following criteria will have to be met:
- The size of the new frame should be the same or close to that of the old one.
- The spacing between the dropouts of the frame should match that of the old frame. Otherwise, the wheel can’t be secured to the frame.
- The headtube of the new frame should be compatible with the fork.
The downsides of this approach are:
- The user has to remove all components from the old frame and install them on the new one. This is a labor-intensive task, and there’s a high chance that some parts won’t be compatible with the new frame.
- A decent frame isn’t cheap.
- The rear brake doesn’t provide as much stopping power as the front brake. Thus, you will only be getting partial benefits.
Option 3: Adapters
Another option would be to get disc brake adapters. Those are brackets usually secured to the axle and the frame or fork. The main downside of disc brake adapters are:
Unsightly. People who want their bikes to be as aesthetic as possible probably won’t like them.
Compatibility. Not every adapter will work with every frame or fork. In some cases, there will be major incompatibility issues.
Tricky. Since the adapter is secured to the dropout, this creates inconvenience when removing the tire.
Questionable functionality. While there are some fine adapters, there are also many that do not provide the necessary strength and functionality for satisfactory performance.
FAQ: Is it possible to weld disc brake mounts to a frame or fork?
In theory, the answer is yes. But in practice, welding disc brake mounts to a frame or fork is not as simple as it may seem.
Below is a number of problems that could be encountered:
The heat produced during welding can alter the integrity of aluminum. Thus, cracked aluminum frames that have been repaired/re-welded require additional heat treatment to restore the area’s strength.
If disc brake mounts are added to an aluminum frame, heat treatment will also be needed.
The full procedure may cost more than buying a used or maybe even a new frame.
Moreover, it’s harder to find welders willing to work with aluminum. The main reason is that aluminum requires expensive welding equipment.
- Lack of Strength
Disc brakes generate more torque. Thus, a frame or a fork originally built for V-brakes may not have the necessary strength to operate with disc brakes. The outcome could include a bent frame or fork.
To fight this issue, some people weld an additional arch between the seat stay and the chainstay on the disc brake side.
However, when it comes to the fork, there’s no way to reinforce it. If it’s weak, it won’t be able to take a disc brake. Hence why it’s not advisable to weld disc brake mounts on thin road forks.
If you don’t have experience welding thin tubing (bike frames and forks), you will have to pay a professional to do it.
The labor will include the following:
- Remove the old paint at the location where the disc brake mounts will go.
2. Fabricate disc brake mounts from a steel sheet.
3. Weld the disc brake mounts to the frame and or fork.
4. Reinforce the frame
5. Repaint the area
The entire procedure is fairly long and requires lots of measuring and a great number of tools.
In the end, the bill may end up being too high to justify the “adventure”.
- Lack of Clearance
Since the frame isn’t designed for disc brakes, it may be too narrow for a rotor over 140mm.
FAQ: Can I use my V-brake levers for my disc brakes?
The short answer is yes if the disc brakes are mechanical. You can find more information on the topic here.
FAQ: What are the advantages of disc brakes over V-brakes?
The main advantages of disc brakes over V-brakes are:
- The stopping power isn’t reduced in wet weather because the disc rotor doesn’t get as contaminated as the rim.
- Disc brakes do not restrict the bike’s tire clearance.
Summary: What You Need To Know
- A V-brake bike can be converted to disc brakes if the fork and/or frame already have disc brake tabs.
- If the frame or fork don’t have disc brake mounts, the options are:
- Get a new fork (the simplest and yet most effective method)
- Get a new frame (labor-intensive without giving you top stopping power)
- Weld a set of disc brake mounts to the fork or frame (expensive and non-practical with aluminum bikes)
- Use a set of disc brake adapters (unsightly and with questionable effectiveness).