This post compares the advantages and disadvantages of U-brakes and V-brakes in relation to each other.
The Advantages of U-Brakes
U-brakes have a slimmer profile than V-brakes. Consequently, it’s easier to install them on the underside of a BMX’s chainstays.
This is a strategically chosen location protecting the brakes during a crash and allowing a streamlined cable routing under the downtube.
Normally, this setup is found on freestyle bikes due to the increased risk of direct mechanical damage to the bike.
- Easier To Use With a Gyro System
Some BMX bikes are equipped with a gyro system a.k.a. a detangler that allows the handlebars to make 360-degree spins.
Without the gyro, the brake cables will wrap around the handlebars and prevent the rider from performing tricks such as bar spins.
To understand why U-brakes are easier to setup with a gyro, it’s necessary to have a basic understanding of a gyro’s mechanism.
The Mechanism of a BMX Gyro
A gyro /rotor/ setup consists of:
Upper cables – the cables attaching to the brake levers and the top plate
A top plate – the plate that sits at the highest point of the gyro
A middle plate – the middle plate is the one that makes the magic happen. The top part connects to the upper cables and the top plate; the lower part is attached to the lower cables and the bottom plate.
The upper and lower part of the mid-plate have a bearing system between them. As a result, the upper part can rotate independently. (The lower part remains stationary.)
When the rider squeezes the brake, the upper cables pull the upper part of the middle plate which in return pulls the lower part of the middle plate and consequently the lower cables too.
Lower plate – the lower plate serves as a holding point for the lower cables. It remains stationary.
Lower cables – the low cables connect the gyro to the brake.
Gyros use a dual brake cable so that the upper part of the mid-plate can pull the lower part of the mid-plate symmetrically and with sufficient force.
For that reason, U-brakes with a dual cable set-up make the installation of a gyro set-up easier and more streamlined.
A V-brake can technically be adjusted to work with a gyro too, but a lot more tinkering is needed since it isn’t a center-pull brake. As a result, most people avoid using a V-brake with a rotor system.
Note: There are also center pull U-brakes that use a single pull cable combined with a straddle cable just like cantilever brakes. Those models are fully compatible with a gyro setup too. The only difference is that the user has to connect the lower gyro cables to the straddle cable which then pulls both arms of the brake.
Cable Pull Differences Between U-brakes and V-brakes
Another property that makes V-brakes non-compatible with standard gyros is their cable pull. (The term cable pull refers to the amount of cable that the brake lever has to pull for the brake to operate properly.)
Since V-brakes have a greater mechanical advantage they need brake levers pulling more cable. Conversely, U-brakes have a smaller mechanical advantage and require brake levers that pull less cable. Hence why V-brakes are called long pull brakes whereas U-brakes are short pull.
A V-brake lever has to pull about 15mm for the brake to engage whereas a U-brake lever needs to pull only 7mm. For that reason, V-brakes and U-brakes need different levers.
The short pull of U-brakes makes them better for a gyro system because the mechanism doesn’t have to pull a lot of cable to initiate braking. Meanwhile, the long pull needed by V-brakes is a problem.
A gyro system combined with a V-brake will result in poor braking unless there’s a converter such as Travel Agents allowing the use of a short pull lever with a long pull brake. In that case, however, the braking system will become incredibly complex due to the high number of involved mechanisms.
For the sake of simplicity, it’s wiser to simply use U-brakes.
Note: If you want to learn how the mechanical advantage of a brake affects the cable pull required for the proper operation of the brake, check out this post.
The Advantages of V-Brakes
- Greater Stopping Power
V-brakes have longer brake arms and a more advantageous pulling angle – qualities resulting in a greater mechanical advantage (leverage). Or in simpler words, V-brakes grab the rim harder for the same effort.
The additional stopping power is the main reason why V-brakes are found on race BMX bikes.
Since those BMX models aren’t used for freestyle stunts, the noodle and the cable sticking out on one side aren’t considered a problem.
V-brakes are used on MTBs, commuting bikes and hybrids. The high demand for the product increases the supply. Consequently, the user can choose between many models.
- Easier Setup
For many people, V-brakes are easier to set-up than center-pull brakes (cantilevers, u-brakes…etc.) due to the fewer settings that the user has to play with. Thus, V-brakes can be seen as beginner-friendly.
That said, u-brakes are not insanely complicated either. They simply require a bit more tinkering.
The Disadvantages of V-Brakes
V-brakes are larger and have a metal noodle sticking out. Consequently, the rider’s body may hit the protruding part of the brake. The outcome could be a failed trick or even a fall.
Since BMX bikes have small frames, full-size V-brakes are difficult to install on the underside of the chainstays due to the lack of real estate.
- Unfriendly To a Gyro
V-brakes are not designed for a gyro setup for the reasons presented above.
Summary: What You Need To Know
The pros of U-brakes are:
- A slimmer profile making them compatible with freestyle BMX bikes.
- Center-pull action facilitating the installation of a gyro system
- Compatible with short pull levers (those operate better with a gyro)
The cons of U-brakes are:
- Lower availability due to limited demand
- Less stopping power due to the smaller mechanical advantage
- Tricky to adjust properly
Conclusion: U-brakes are the go-to choice for freestyle BMX bikes, but they make little sense when the bike is used for speed (e.g., BMX racing).
The pros of V-brakes are:
- Great stopping power
- A huge variety of models
- Easier to adjust
The cons of V-brakes are:
- A bulky setup that may come in contact with the rider’s body.
- Difficult to use with a gyro system due to the pulling mechanism and the long cable pull needed for proper braking
Conclusion: V-brakes are better for bicycles designed for speed.