Brake Disc Parts, Types and Functions

So many brake components come into play when stopping your vehicle, one of which is the brake disc. The brake disc, also called the brake rotor, is located on the wheel hub and spins with the wheel. It provides the friction needed to stop your wheel. When the brake lever is pressed, hydraulic pressure squeezes the piston against the pads, which in turn squeezes against the brake disc rotor, creating friction.

This action results in slowing down of the rotors. And because the rotor connects directly to your wheels and spins along, your wheel slows down or stops as the rotor does. Rotors are available in different sizes. And usually, the larger the size, the larger the surface area, which improves performance and longevity. The brake disc, however, comprises components that help it function well. But before we discuss brake disc parts, let’s learn about the types of disc brakes.

types of disc brake

Types of brake disc

Braking systems tend to improve performance over the years as vehicles improve. The need for greater speeds, greater vehicle size, and weight has led to the production of more improved braking parts. Hence, the different types of brake discs.

Flat or plain brake disc

Flat brake discs have a flat smooth surface usually made with iron and are attached to a car’s wheel hub. These types of brake discs are light weighted and, as such, commonly used in many small vehicles to do the job perfectly. And are inexpensive to manufacture and replace.

They have a large surface area which enhances better contact with the brake pads, allowing excellent braking. However, it can lose its braking capability during longer braking periods. They are also prone to building up heat quickly, damaging them when the heat becomes too high. Lastly, the disc gets weakened when drilling the holes, which could cause faster damage.

Vented brake disc

Generally, the bigger and heavier a vehicle is, the more load the brakes take, which means more heat is generated. Vented brake disc has a higher heat-dissipating capacity. So as the car generates heat, this brake disc quickly whisks it away to prevent damage, invariably extending its life span.

This brake disc successfully removes brake heat, thanks to its vented design. Through these vents, heat generated leaves quickly. Vented brake disc, however, due to its design, has a slight increment in weight, invariably adding to the car’s weight.

Drilled brake disc

These brake discs have holes drilled into their surface, invariably increasing the surface area. Through these holes, heat, gas, and other materials are quickly expelled from the disc, hence preventing build-up on the contact surface. Another advantage of these holes is that it makes the disc a bit lighter because of disc material lost during drilling.

However, while these holes quickly expel heat and foreign bodies, they can also be a medium through which dirt and other bodies build up on them. They are also susceptible to cracks and warps under high temperatures. While the drilled holes don’t tamper with their stability, it reduces their heat-taking capacity once it exceeds the amount they can expel efficiently.

Slotted or grooved brake disc

These brake disc surfaces can be grooved or slotted, just like drilled discs. Through these grooves or slots, heat, gas, and other foreign elements are quickly expelled. But unlike drilled brake discs, their heat resistance is not compromised.

While not as common as drilled discs, they last twice as drilled brake discs. The grooves are of various sizes and depths and are stationed at the center of the disc at a certain position to expel foreign elements as the disc spins. They are, however, noisier since the grooves rub on the pads.

Slotted-drilled brake

These brake discs have both slots and holes on them. They work to maximize the benefits of both drilled and slotted disc types while minimizing their drawback.

On this brake disc, the number of holes is reduced, which helps them maintain its high resistance to heat while still expelling heat or waste. In the same vein, by reducing the number of slots, noise is also reduced while still letting the slot rub against the pad.

Dimples brake disc

Dimpling particularly helps reduce disc weight without reducing its structural integrity and resistance to heat. However, the absence of holes does reduce their heat-expelling capacity. Nevertheless, the dimples allow friction material to escape the surface before being whisked away by air.

Waved edges brake

This brake disc utilizes a wavy edge in a bid to reduce weight while not tampering with its stability, resistance to heat, and performance. Instead of the plain circular shake, this brake disc is shaped like a wave. Waved-edge brake discs are a good fit for performance vehicles and perform better than plain circular discs.

Brake disc parts

The brake discs comprise several components working in synchrony to help stop your car. However, the following are the main disc brake parts and functions.

Wheel hub

The wheel hub is where your vehicle’s wheel is attached to. Your brake rotor (disc) is attached to the wheel hub and spins along with it.

Caliper assembly

The disc brake caliper is directly connected to the disc rotor. These components, however, house many other components, such as

  • Brake pads: which push against the rotor creating friction to slow or stop your car
  • Piston: that supplies brake force on the brake pad when the brake lever is applied
  • Slide pins: allow the caliper to move smoothly and keep it in place
  • Dust boots: act like a filter and help in preventing dust and other particles from contaminating the cylinder bore, slide pins, etc
  • Piston seal:  that helps keep the brake fluid in its place
  • The caliper bracket: is attached to the wheel knuckle and supports the entire caliper assembly. It bears all the braking weight

Disc brake rotor

The disc brake rotor connects directly to the wheel hub and rotates as the wheel rotates.  The disc rotor, when pushed by the brake pads, creates friction to slow your car. The rotor is circular and made with cast iron, and in high-performance cars, they are built with composite materials such as carbon fibers or ceramics.

Generally, the disc rotor generates a lot of heat during braking, which invariably reduces braking efficiency. For this reason, the disc rotor has ventilation holes that help dissipate heat for better braking performance. Some rotors have only directional vanes and, as such outfitted to only one side of the car.

disc brake assembly


Q: What are the three major parts of the disc brakes?

The three major parts of disc brake are the wheel hub, caliper assembly, and disc rotor. The hub connects to the wheel, which moves your car, with the disc rotor also connected to it. So basically, the rotor spins as the wheel hub spins. The caliper assembly houses the piston and brake pads.

When the brake pedal is pressed, hydraulic pressure created by the master cylinder pushes the piston against the brake pads. The brake pads then push against the disc rotor, creating friction. This friction created slows down the rotor, invariably slowing down the wheel hub since both of them spin together. Therefore, the rotor slows down or stops, so does your car.

Q: What parts are usually replaced on the disc brakes?

Virtually all parts which help your disc brake work can be replaced when faulty. The disc brake system utilizes many components when slowing or stopping your car. So during a brake job, check the conditions of all the parts, from the brake caliper, brake pads, rotors, slider pins, etc. And replace or service as needed.

However, most of the time, the parts with a higher chance of being changed during a brake job are the rotors and brake pads. This is true because of the job and connection. If the rotor has any wear grooves, chances are the brake pads too, won’t sit properly on. While the pads will work, they won’t last long. In summary, while the rotor and brake pads are mostly replaced during a brake job, also access the conditions of other parts.

Q: What is disc brake assembly?

The disc brake assembly entails all parts of the disc brake. They include the wheel hub, caliper assembly, and disc brake rotor.

The wheel hub has the wheel and rotor attached to it. The caliper houses the brake pads, pistons, slider pins, and other caliper parts. The rotor connected to the wheel hub creates friction to stop your car.

The disc brake is a kind of braking system in cars, with most disc brakes operated hydraulically. There are two types of disc brakes—floating and opposed piston. While the floating, also called sliding disc brake, uses pistons on only one side of the rotor, the opposite-piston disc brake uses pistons on both sides.

Q: How many brake discs does a car have?

How many brake discs a car has depends on the car’s age. Cars manufactured after 1970 may have two disc brakes placed at the front wheels with two drum brakes at the back wheels. However, some have brake disc rotors on all wheels. So practically, cars have either two or four disc brakes.

Q: What type of brake disc is the best?

Which brake disc is the best depends on personal choice. Each of them is meant for certain conditions and also has its downside. So pick the one that almost meets your needs. Small vehicles will do well with the flat brake disc due to their lightweight.

Whereas bigger or heavy vehicles likely to generate more heat will do well with vented brake discs since they have a high heat dissipating capacity without compromising the life span. So, it typically depends on your vehicle and preference; cars and bikes won’t need the same brake discs.


Brake disc parts collectively work to bring your car to a stop, so ensure all parts are doing fine. Generally, each vehicle has a certain brake disc that fits and functions as needed. However, purchasing the right type isn’t enough; also, ensure you purchase a good brand.

You can check the Bendix air disc brake parts catalog for options. The Pulsar 150 disc brake spare parts are also a good option. In all you do, only get the parts that match your car’s performance. Else, you will be changing the brake disc earlier than required.


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