Debates aside, and beyond controversies regarding their use in high-level competition, disc brakes dominate the cycling market. If you want to show off a fully updated bicycle, it should be equipped with this type of brake. In this guide, we tell you everything about how they work and current technologies. We will also share simple (but effective) tips for their care and maintenance.
The disc brake system: parts and operation
Let's start by refreshing some basic concepts. What are the components of disc brakes?
Brake lever
The construction will be different depending on whether the braking system is hydraulic or mechanical. If it is hydraulic, a small reservoir or pump with brake fluid inside (mineral or synthetic oil, depending on the brand or model) will be attached to its body. By pulling the brake lever, pressure is applied to this fluid, moving it to activate the brake calipers. If the system is mechanical, there will be no pump or reservoir. The same action performed by the fluid is instead done by a braided steel cable, which gains or loses tension depending on how much the lever is squeezed.
Calipers
Before the fluid directs that pressure onto the caliper and brake disc, it travels inside the hose or cable until it reaches the caliper's piston. This, in turn, moves to press the brake pads, the other internal element of the brake caliper. Currently, two types of calipers can be distinguished:
- 2-piston. These are the most common in all cycling disciplines. The two pistons are located on either side of the caliper, behind the corresponding pad.
-
4-piston. These are mainly used in more extreme MTB disciplines, such as Enduro
or Downhill
, although they are increasingly common in Cross Country
, hardtail bikes
, etc. In this case, the number of pistons is doubled: two on each side of the caliper to provide more braking power with the same or similar modulation.
On each side, the first piston located in the direction of the disc's rotation is smaller than the second. This compensates for the wedge effect or greater braking force that occurs in the area. This way, the pad does not wear more on one side than the other and disc oscillations are eliminated.
4-piston brake calipers can increase braking power by up to 20%.
Four-piston calipers are larger and about 20-40 grams heavier than two-piston ones. They are only compatible with specific 4-piston brake models and are more expensive: about 50 €, on average.
Brake pads
When we refer to brake pads, we are talking about the metal component responsible for stopping the rotation of the disc and braking the wheel. This is a crucial part with a limited lifespan, and its wear should be checked frequently. We can distinguish two main types, depending on the compound used for the braking surface: organic (better braking but shorter lifespan) and metallic (slightly less perfect braking, but more durable).
Discs
Depending on their size (diameter) and construction (one-piece or two-piece), they will enhance certain properties over others.
1.- The diameter of the discs Determines the braking capacity. A disc with a larger diameter will generally minimize the time from when the lever is pressed until the wheel stops. On the other hand, an increase in disc diameter is recommended to handle the greater power of a specific brake. For example, a four-piston brake will require large diameter discs to better handle and manage this power. Next, let's review the different diameters available on the market.
- 140 mm: currently the smallest standard. Mostly found on road or cyclocross bikes.
- 160 mm: intermediate size, the most used and versatile: MTB cross country, road, or gravel.
- 180 mm: more typical for MTB (as a front brake disc) and in disciplines with high braking demands: XC/trail or enduro.
- 203 mm: mostly found in more radical MTB disciplines: trail, enduro, and downhill.
- 220 mm: specific disc for enduro and downhill bikes, especially on the front wheel.
A larger diameter disc tends to minimize the time between pulling the brake lever and the wheel stopping.
2.- The design and construction of the discs Depending on their design and structure, the disc can be more or less heavy and better withstand the heat and fatigue from braking. In this sense, we can distinguish two categories: rigid discs and floating or two-piece discs.
Rigid discs consist of a single piece of stainless steel. They are the most common, found on entry-level and mid-range bikes. Also on high-end bikes with special designs to dissipate heat.
Floating or two-piece discs have an external or braking surface made of steel, along with a core made of a lighter material that is more resistant to heat (aluminum or carbon). They are more expensive than rigid discs and are installed on mid- and high-end bikes, both road and MTB.
On the other hand, it is important to consider the type of hub mount, since there is no universal one, and it is important to determine compatibility with the bike. Two mounting standards can be distinguished: 6-bolt (mainly SRAM) and Center Lock (threaded, patented by Shimano). Most brands have models with versions for one or the other system.
Types of disc brakes
To classify disc brakes, we can look at two criteria: according to their actuation and according to the cycling modality.
According to their actuation
We have already mentioned that there are two universal disc brake systems according to their actuation technology: hydraulic and mechanical.
1.- Hydraulic disc brakes This is the most widespread system. The braking circuit is filled with brake fluid (a mineral or synthetic oil) that is pumped from the lever to the caliper. Among its strong points is its more progressive and modulated braking, from less to more, which prevents wheel lockups to favor better control.
2.- Mechanical disc brakes Mechanical disc brakes use a traditional brake cable. The braking is somewhat more abrupt, less progressive. In addition, they tend to become misaligned more easily and lose feel. However, repairs and adjustments are simpler than with a hydraulic brake. It does away with the cumbersome system bleeding and fluid replacement.
➡️ Hydraulic or mechanical disc brakes: what are the differences?
According to modality
Another criterion for classifying disc brakes is to consider the cycling modality you practice.
1.- Mountain Bike Disc brakes arrived in mountain biking
more than 20 years ago, as a response to increasingly technical routes and the need for more effective and controlled braking. The disc standard ranges from 160 to 220 mm, and the lever is straight and reach-adjustable (without tools on higher-end models). In addition, it is also possible to improve power with four-piston models.
2.- Road Road disc brakes
, more recently introduced, have their own particularities in levers, caliper size, and disc diameter. They are smaller than MTB brakes (140 and 160 mm), and the floating type is becoming more popular than the rigid ones, with a more extended and opaque central piece, as well as fins to better dissipate heat (Shimano Ice technology).
3.- Gravel Disc brakes for Gravel
have similarities in sizes and technologies with road ones, using the same type of lever for the drop handlebar. But the disc diameter is usually larger, opting for 160 or 180 mm. In addition, the brake levers have a different design and ergonomics that provide a better finger grip, sacrificing a bit of weight.
Technologies: new trends
Do you want to learn about some of the new technologies that are becoming popular in current disc brakes for cycling?
Levers: adjustable in reach and contact
This is a system found in mountain bike disc brakes, such as the SRAM G2. In addition to the more common adjustment of the lever's position relative to the handlebar (using a small wheel), there is another wheel or dial integrated into the lever body that regulates the contact point with the pad. It affects the lever travel, providing a firmer or softer feel without moving the pad's position.
Calipers: four pistons and rigid
Four-piston caliper brakes have broken the boundary of competition and the most extreme MTB disciplines. Major brands already offer models for all types of mountain bikes, and in all price ranges. The rise of e-bikes
, which require stronger and more powerful brakes, has also contributed to this expansion. Calipers feature designs that provide greater integration and rigidity, ensuring uniform braking without vibrations and preventing caliper movement or misalignment.
Mount: Flat Mount
The front and rear brake calipers of many mid- and high-end bicycles, both road and MTB, are now mounted with the Flat Mount system. This eliminates the need for a caliper adapter to bolt it to the frame's Post Mount anchor, saving a few grams, achieving better integration with the bike, and greater rigidity in the braking area.
Caliper and disc cooling
Overheating of disc brakes, especially from continuous use (mainly on descents), causes system fatigue, loss of feel, and power. Manufacturers are constantly working on technologies that allow better heat dissipation from discs and calipers, the areas where temperature rises the most.
In calipers, aluminum pistons are becoming the solution to overheating.
Shimano has perfected its Ice technology, now called Ice Freeza for its most advanced brakes (Dura-Ace, Ultegra, XT in MTB, etc.). It focuses mainly on the discs, adding steel or aluminum fins (depending on the model) in the center to dissipate heat. It also adds a thin layer of aluminum in the body and braking track, a material that retains less heat than steel, as well as a special paint coating capable of reducing the temperature by 10º C. For its part, SRAM launched its HS2 discs for Mountain Bike in 2021. They are floating type and have the particularity of having ribs with a special black paint coating that can lower the temperature by up to 40º C under the most demanding braking conditions.
Likewise, increasing the disc thickness from 1.85 to 2 mm, in this case, always results in reduced heating due to the use of more material.
Maintenance: basic care to avoid breakdowns
Bleeding the fluid is one of the most important operations required for good disc brake maintenance; not to mention replacing the pads, of course.
Bleeding
You should do it once a year, whether you use your bike a lot or not. Brake fluid loses its properties both with use and without it, so it will be necessary to extract the old fluid by pumping new fluid from the lever toward the caliper outlet. In principle, it is a simple operation that you could do at home, but you will need two small hoses, a funnel, and brake fluid to perform the bleeding.
➡️ 5 common brake issues on your bike and how to fix them
Pad replacement
The pad compound wears away due to friction with the disc. You should check their condition frequently, every two or three months. If their thickness is less than 1 mm, you should consider replacing them; if it drops to 0.5 mm, you must replace them immediately, as the metal backing of the pad (which is harder) will start to rub against the disc, damaging its braking surface. You can remove the caliper and, using its metal bridge, take out the pair of pads to check for wear. You can do this operation together with the annual bleeding to better organize your brake maintenance. The cost of the pads is not very high, ranging from 10 to 20 euros. You can change them at home without much trouble, saving yourself a good amount of money on workshop labor.
➡️ All about brake pads: types, materials, and maintenance
Caliper alignment
Hard braking, impacts or falls, or simple use, can cause misalignment in the caliper's attachment to the frame or fork (in the case of the front brake). This causes the pads to be off-center with respect to the disc, which creates friction even without engaging the brake. To avoid the annoying noise this causes, and to reduce pad wear from these rubs, loosen the caliper mounting bolts. Move and slightly center it, squeezing the lever at the same time to realign them with the disc, and retighten the bolts, alternating tightening to ensure even pressure on both sides.
Cleaning: calipers, pads, and discs
Clean brakes—discs, calipers, and levers—before each ride will work more efficiently and add years to their lifespan. A superficial cleaning with water and soap, making sure it does not get inside the caliper, is required after every ride.
To clean the inside of the caliper, which is advisable to do monthly, you should first remove the pads. Then, clean the inside with water and neutral soap, or a specific disc brake cleaner. Finally, lubricate the surface of the pistons with the same brake fluid used in the system.
Disc brakes should be thoroughly checked once a year, with fluid and pad replacement.
As for the brake pads, check that the compound has no dirt, oil, etc. Otherwise, they will be contaminated and it will be necessary to treat them with water and alcohol, and then gently sand them to remove these residues. If you don't do this, braking efficiency will be compromised, as well as the feel when braking. Cleaning the braking surface of the disc is also essential. Do this after every ride with a soft cloth (microfiber), a little water, and neutral soap. There are also disc cleaners on the market, which additionally have dust or mud repellent properties.
Don't forget the initial bedding-in
Finally, some advice for cyclists who are not very familiar with disc brakes. To begin with, the feel, power, and modulation of braking is different from that of rim brakes. Therefore, prior adaptation and bedding-in are required. In this regard, when buying a new bike with disc brakes, or after each pad change, you must carry out a bedding-in or acclimatization process for the system. Since the surface of the new pad compound is so firm and polished, they will slide over the disc and not stop it, increasing the risk of an accident.
After each pad change, it is advisable to carry out an adaptation process on the bicycle.
Thus, you need to pedal and gradually apply the brake, from less to more, repeatedly, on a flat or low-traffic street, in a controlled manner. We recommend doing this until you feel the brake lever becomes firmer and the bike stops more quickly each time. You can also do this bedding-in while stationary, placing the bike on a stand with the wheel suspended in the air and braking repeatedly until it firms up. With this bedding-in, we also ensure that the pads are aligned with the disc and wear evenly across their entire surface.