Is It Time To Go Disc?

There’s no escaping the inevitable progression of BMX Racing technology. While disc brakes have solidified their place at the top of the food chain within other disciplines, we are just now seeing the integration of these Braking systems into BMX racing. 

New tech is always exciting, but it can also be confusing. With more and more frames becoming Disc brake compatible, it’s clear to see that V-Brakes are on their way out. However, there’s a lot of variation between disc brakes as the platforms became tailored towards different disciplines of cycling. 

Today, we will discuss the various Disc Brake options on the market while touching on the pros and cons of each type. At the end, we’ll leave you with our personal recommendation for what we believe to be the optimal disc brake for BMX Racing. Throughout the article, we’ll also touch on the distinctions between Disc and V-Brakes as we try to determine which is the better platform for BMX Racing.

But first…

What is a disc brake?

A Disc Braking System applies friction to a Rotor attached to the Rear Hub. A Caliper mounted to the Frame or Adapter, houses two Brake Pads which contact the spinning Rotor producing deceleration (braking).

Whereas Traditional Braking Systems apply friction to the Rear Rim during deceleration; Disc Brakes do not contact the rear rim since friction is only applied to the Rotor.

Variations in disc brakes

There are two primary distinctions between Disc brakes, Hydraulic and Mechanical. Both systems incorporate a Rotor, Brake Lever, and Caliper with Pads. The primarily difference between the two systems is how force is applied from the Brake Lever to the Caliper. 

Hydraulic Disc Brakes 

Hydraulic Brakes use an Oil Based system to initiate contact between the Pads and Rotor. When you squeeze a hydraulic Brake Lever, a Plunger pushes Brake Fluid from the Master Cylinder (the lever body), into the Brake Line. Since the Brake Line is sealed and already full of fluid, the incoming fluid from the Master Cylinder creates pressure which pushes the Pistons within the Brake Caliper. These pistons push the Brake Pads into contact with the Rotor creating friction thus slowing the bike down. 

Hydraulic disc brakes feature the same technology used in car and motorcycle brakes. 

Pros of Hydraulic Brakes

• More stopping power/ more efficient
• Less frequent maintenance since the braking system self adjust
• System is sealed keeping contaminants out

Cons of Hydraulic Brakes

• More expensive
• Harder to service as the system requires specialty tools
• More prone to rear wheel lock ups

Mechanical Disc Brakes

Mechanical Disc Brakes are a closer relatives to traditional braking systems. Mechanical brakes actuate with a steel cable, just like Rim Brakes and even use the same levers as Rim Brakes. When you pull the Lever, it pulls a Cable that runs to the Brake Caliper Arm. The Cable moves the Caliper Arm which pushes a Piston within the Caliper. The Piston pushes the Brake Pads against the Rotor to create friction that stops the bike.  

Pros of Mechanical Disc Brakes

• Cheaper than hydraulic brakes
• Easier to repair due to more simplistic construction
• Replacement parts are easier to find 
• Less likely to lock up the rear wheel

Cons of Mechanical Disc Brakes

• Less stopping power than hydraulic brakes
• Require more frequent adjustments as cable begins to stretch 
• Friction within the brake line can produce inconsistent braking

Why are people using them? 

Advantages of disc brakes includes

•  Increased Stopping power
•  Better modulation (more brake control)
•  More Consistent braking
•  Improved reliability in all weather conditions

Disc brakes generate an incredible amount of stopping power, usually far more than what’s actually needed for BMX applications. But the idea isn’t to lock up the brakes with every pull. The increase in power allows for more efficient braking so riders can apply less force to the lever and still receive sufficient stopping power.

For someone just starting out with disc brakes, the stopping power can be overwhelming. Over time, the rider adapts to the short lever pull and learns how to tap the lever whereas rim brakes would need a much longer pull. Less time on the brakes = means more time increasing speed!

Another advantage of disc brakes is increased predictability and control. Pulling with a measurable amount of force on a rim-brake lever can lead to inconsistent results. Depending on how dirty or clean the rim braking surface is, the amount of stopping power you receive with each lever pull will be different. Disc brakes provide more consistent stopping power with each pull. While disc brakes are far more capable of locking up the rear wheel, they also provide more lever-feedback meaning an aware rider is less likely to lock up.   

Building off of the point about consistent braking, Disc brakes are also far more reliable in inclement weather conditions. While 95% of the time, BMX Racing is done in dry conditions, those rainy race days will cause real havoc for rim brake users. When applying a rim brake in wet conditions, there will be a split second delay before deceleration begins. This delay is due to the brake pad displacing water and grime from the brake track. That split second delay can be the difference between a severe crash or a close moment.    

A more indirect reason for the rise of disc brakes is the increased number of Carbon Rims. Over time, rim brakes can erode the protective filament on a Carbon Rim’s brake track. As the filament deteriorates, the pads will start to eat away at the carbon eventually leading to component failure. Since disc braking systems use a Rotor in place of the rim, racers can run whatever rims they want without a concern of eroding Carbon.

However, Carbon Brake Pads have come a long way over the years and do a better job of preserving the rim through increased heat dissipation capabilities. So the concern about rim brakes on carbon hoops isn’t as large as it once was, however, it’s still something to take note of.

Where Disc Can Go Wrong

We’ve talked a lot about the advantages of disc brakes and it may seem as though the clear choice is to go disc. But there’s still some fundamental flaws with the systems when used for BMX applications. 

Simply put, The current Disc brake offerings are far too powerful for BMX Racing, and here’s why.

Hydraulic brakes posses the most stopping power on the market and are designed to stop a 26 inch or even a 29 inch wheel. These much larger wheel bases carry far more momentum and require a greater stop force to effectively decelerate. This need for greater braking power is what generated the idea of hydraulic braking systems. 

Secondly, these mountain bike focused braking systems (disc brakes) are designed to pair with heavy, knobby, pliable, mountain bike tires often ran at pressure of 25 - 40 PSI. As the wheel starts to lock up during deceleration, the mountain bike tire compresses and increases it’s contact patch with ground providing even more traction.

When you attach the same Mountain Bike designed brake caliper onto your 20 inch race bike, it’s clear to see how problems arise. BMX wheels are exponentially smaller and lighter than mountain bike wheel. The extreme braking power of a 4 piston hydraulic brake quickly locks up the rear on any BMX bike.

Remember that these calipers are intended to work with pliable mountain bike tires. So a slick tread, 110 PSI Racing Tire cannot provide the same compression and expanding contact patch that a mountain bike tire can. As the wheel locks up… the wheel locks up! There’s little to no give in a BMX Racing tire because of the high tire pressures. Controlling the modulation of a disc brake proves to be challenging when paired with BMX Race bikes as the system is too strong for the small, light wheels. 

All of this to say, that while Disc brakes provide an array of advantages and truly are a superior braking system. The problem still remains that these systems are not designed for a 20 inch wheel base. 

Where Do We Go From Here?

So what’s the solution here? Or rather, what do we recommend?

The clear answer is to develop a disc braking system designed specially for a 20 inch wheel base with stiff tires. However, we are not provided that luxury, at least not yet. 

Our current recommendation is to find the lightest brake possible. Not in terms of weight but braking power. If you feel as though you absolutely HAVE to go disc right now, then we suggest a Mechanical Disc Brake. Not only are these systems easier to work on and cheaper, but they’re also less powerful than hydraulic systems. You’ll have more control over the application of braking force and won’t be thrown over the bars as easily by snappy hydraulic brakes. 

If you love the shiny, luxurious, expensive hydraulics and just have to have them; Then we suggest you look into any of the 2 piston XC Hydraulic Brake. These are the lightest hydraulic systems in both terms of weight and stopping power. But use caution during your first few rides as you begin to develop an understanding for how strong these brakes really are. 

We can’t forget about the Rotor too as these components come in various sizes. Regardless of which disc system you choose, we will always suggest the smallest Rotor possible. The 120mm Rotors seem to work the best for BMX as bigger Rotors increase the stopping power. Again, these systems are already too strong for BMX application so you should take all measures to decrease the stopping power. We have found the smaller 120mm Rotor to be the most viable option.

With all this talk about brakes, we need to remember that a Race bike is a Racing machine with no intentions of slowing down. We still run brakes for safely purposes, but ideally you want to stay away from that lever during a hot lap.

We believe that disc brakes are the future as we have multiple disc compatible frames in our store, but we also feel that the technology isn’t quite there yet. Until there’s a BMX specific disc brake system, we will always favor V-brakes as the better alternative. V-Brakes are proven to work and provide the necessary stopping power for BMX Racing.

The largest concern with V-Brakes is failing under wet weather conditions, but as we’ve previously established, it’s a rare occurrence to be riding your bike in a thunderstorm. Disc Brakes are great and provide an advancement in BMX technology, but since the platforms aren’t designed for our specific application, the cons outweigh the pros. Once the industry gets their hands on BMX specific Disc Brakes intended to pair with Racing Tires and 20 inch wheels, then may it be the end of V-Brakes as we know it. But until then, we do not see the over powered Disc Brakes of today as a better option over milder V-Brakes in most scenarios. 

-  Written by: Jonnie Vance