The first component of the car drum brakes is the wheel cylinder. A wheel cylinder is
located in each wheel. It is usually positioned at the top of the wheel, above the shoes.
The wheel cylinder function is to exert force onto the shoes to contact the drum and
stop the vehicle with friction.
Wheel cylinder consists of several components such as:


Wheel cylinder housing; is a place for all wheel cylinder components, including
brake oil
Pistons; The drum brake pistons function is to change the hydraulic pressure to

be mechanical movement. They are connected to the brake shoes.
Piston seal cups; The piston seal cups function is to keep the hydraulic



pressure of brake oil from leaking.
Piston boots; The piston boots function to protect the pistons from dust and
debris and prevent rust.
Return spring; Returns spring function is to bring the pistons back to their
positions, so the pistons are always in contact with the brake shoes.
Bleeder nut; The bleeder nut functions as an air drain from the wheel cylinder,
so the wheel cylinder is filled only by brake fluid.
2. Backing plate
The second component of the car drum brakes is a backing plate. The backing plate is
made from a steel plate with a circular design. The function of the backing plate is to
hold the braking system together so it can work properly.
It holds almost all drum brake components such as wheel cylinder, brake shoes,
anchor, adjusting lever, etc. The backing plate is attached to the differential housing or
knuckle arm and being a stationary component.
3. Pins
The third component of the car drum brakes is pins. The pins work together with shoe
hold springs to hold the brake shoe so they can always stick to the backing plate as a
holder.
4. Parking lever
The fourth component of the car drum brakes is the parking lever. The parking lever is a
lever that will activate the brake shoes manually using a brake cable. When the driver
pulls up the parking brake lever inside the car cabin, the parking lever will move and
push the brake shoe manually. So the brake shoe pushes the drum brake and makes
the parking brake active.
5. Anchor
The fifth component of the car drum brakes is the anchor. The anchor is fitted on the
backing plate and has an opposite position to the wheel cylinder. The anchor function is
as a base and pivot for the end side of the brake shoe when they're moves. There are
two types of anchor models, fix type model and moveable type.
6. Brake shoe & linings
The sixth component of the car drum brakes is the brake shoe and lining. Brake shoes
and linings are the main components were used to slow or stop the car. They are
pushes into the drum to create friction. Secured to the backing plate but able to slide
when pressure from the wheel cylinder is applied.
The linings are made up of organic or metallic compounds. The lining is what comes in
contact with the drum and wears away with use. Each brake contains two shoes. The
primary shoe is closer to the vehicle's front, while the secondary shoe is closer to the
rear.
Read also:


#7 Reasons your car pulls left when braking
Brake fluid low signs and causes
7. Adjuster lever
The seventh component of the car drum brakes is the adjuster lever. The adjuster lever
function is to adjust the gap between the brake shoe lining and the inner side of the
drum. The gap is affecting the brake pedal play.
Automatic adjusters adjust the gap by themselves, keeping the brake shoes at a
consistent distance away from the drum. Still, if your drum brake uses a regular adjuster
type, you need to adjust the gap regularly. So if your brake pedal play is too large, then
to reduce the length of the brake pedal play, adjust this adjuster lever.
8. Drum
The eighth component of a car drum brakes is a drum. The drum is often made of cast
iron and is resistant to heat and wear. It bolted to the wheel hub and spun with the
wheel. When a driver applies the brakes, the lining pushes against the inner surface of
the drum. The ensuing friction slows or stops the rotation of the wheel and axle, and
thus the vehicle.
9. Shoe hold spring
The ninth component of the car drum brakes is the shoe hold spring. Shoe hold spring
function is to keep the brake shoes always fitted to the backing plate. The springs work
together with pins.
10. Return spring
The last component of the car drum brakes is the return spring. Return spring serves to
retract the brake shoe & lining position after the braking process takes place, mostly
when the driver lets off the brake pedal.
When the brake pedal is pressed, the brake shoe will move outwards and press on the
brake drum due to piston pressure in the wheel cylinder. And to prevent the brake shoe
from continuously pressing the brake drum, this return spring is used to return the brake
shoe to its original position.
The location of the return spring is generally 2: above (upper spring) and at the bottom
(lower spring). In addition, the two return springs are generally installed between the two
brake shoes.
DISC BRAKES
Brake rotors of disc brakes rotate with the wheels, and brake pads, which are fitted to
the brake calipers, clamp on these rotors to stop or decelerate the wheels. The brake
pads pushing against the rotors generate friction, which transforms kinetic energy into a
thermal energy.


Brakes for Automobiles
Opposed Piston Type Disc Brakes
This thermal energy generates heat, but since the main components are exposed to the
atmosphere, this heat can be diffused efficiently. This heat-dissipating property reduces
brake fade, which is the phenomenon where braking performance is influenced by the
heat. Another advantage of disc brakes is its resistance to water fade, which occurs
when the water on the brakes significantly reduces braking force. When the vehicle is in
motion, the rotor spins at high speeds and this rotational motion discharges the water
from the rotors themselves, resulting in stable braking force.

Getting to Know Brakes｜Products and Technologies

Disc brakes are generally used in passenger cars, but due to their stable performance
at higher speeds and resistance to brake fade, they are gradually spreading into the
commercial vehicle segment, where drum brakes were traditionally chosen for their
longer service life. There is increasing demand from customers for longer service life
and higher quality, and Akebono is committed to meeting them through further
development of the disc brake’s reliability. There are two types of disc brakes.
The "opposed piston type disc brake" has pistons on both sides of the disc rotor, while
the "floating type disc brake" has a piston on only one side. Floating caliper type disc
brakes are also called sliding pin type disc brakes.
Disc brake construction
The brake rotor (disc) which rotates with the wheel, is clamped by brake pads (friction
material) fitted to the caliper from both sides with pressure from the piston(s) (pressure
mechanism) and decelerates the disc rotation, thereby slowing down and stopping the
vehicle.

How disc brakes work
When the driver steps on the brake pedal, the power is amplified by the brake booster
(servo system) and changed into a hydraulic pressure (oil-pressure) by the master
cylinder. The pressure reaches the brakes on the wheels via tubing filled with brake oil
(brake fluid). The delivered pressure pushes the pistons on the brakes of the four
wheels. The pistons in turn press the brake pads, which are friction material, against the
brake rotors which rotate with the wheels. The pads clamp on the rotors from both sides
and decelerate the wheels, thereby slowing down and stopping the vehicle.
Main components of disc brakes
Main components of floating type disc brakes
There are two types of disc brakes. One is called the "opposed piston type disc brake"
which has pistons on both sides of the disc rotor, and the other is the "floating type disc
brake" which has a piston on only one side. The floating type disc brakes are also called
the sliding pin type disc brakes.
Table of Contents

Disc Brake | Construction , Working Principle , types and Rotor Materials
o CONSTRUCTION OF DISC BRAKES





o
1. Rotor:
2. Brake pads:
3. Piston:
4. Caliper:
5. Sensors:
WORKING PRINCIPLE
o
o
o
o
TYPES OF DISC BRAKES
 1. Opposed Piston Type Disc Brakes
 2. Floating Type Disc Brakes
TYPES OF ROTOR
ROTOR MATERIALS
ADVANTAGES AND DISADVANTAGES
Disc Brake | Construction , Working
Principle , types and Rotor Materials
Brake rotors of disc brakes rotate with the wheels, and brake pads, which
are fitted to the brake calipers, clamp on these rotors to stop or decelerate
the wheels. The brake pads pushing against the rotors generate friction,
which transforms kinetic energy into a thermal energy.
This thermal energy generates heat, but since the main components are
exposed to the atmosphere, this heat can be diffused efficiently. This heatdissipating property reduces brake fade, which is the phenomenon where
braking performance is influenced by the heat. Another advantage of disc
brake is its resistance to water fade, which occurs when the water on the
brakes significantly reduces braking force. When the vehicle is in motion, the
rotor spins at high speeds and this rotational motion discharges the water
from the rotors themselves, resulting in stable braking force.
Read also : Seminar On Ceramics Disc Brakes- Report Download
CONSTRUCTION OF DISC BRAKES
The brake rotor (disc) which rotates with the wheel, is clamped by brake
pads (friction material) fitted to the caliper from both sides with pressure
from the piston(s) (pressure mechanism) and decelerates the disc rotation,
thereby slowing down and stopping the vehicle.
Disc Brake
Components
1. Rotor:
Circular disc bolted to the wheel hub that spins with the wheel. Rotors are
most commonly made of cast iron or steel; however, some very high-end
cars use a carbon ceramic rotor. Rotors can be slotted or drilled for better
heat dissipation.
2. Brake pads:
Component that pushes into the rotor, creating the friction that slows and
stops a car. They feature a metal portion called a shoe and a lining that is
attached to the shoe. The lining is what actually comes in contact with the
rotor and wears away with use. Linings are made of different materials and
fall into three categories: organic, semi-metallic and ceramic. The lining
material chosen will impact the length of brake life, the amount of noise
heard when the brakes are applied, and how quickly the brakes bring a car
to a halt.
3. Piston:
Cylinder connected to the brake system hydraulics. The piston is what
moves the brake pads into the rotor when the driver presses the brake
pedal. Some brake systems have a single piston that moves both pads,
while others have two pistons that push the brake pads from each side of
the rotor. Others still have four, six, or even eight pistons for higher braking
power, at the expense of added cost and complexity.
4. Caliper:
Housing that fits over the rotor and holds the brake pads and pistons, as
well as contains ducting for brake fluid. There are two types of brake
calipers: floating (or sliding) and fixed. Floating calipers “float” over the
rotor, and only have pistons on a single side. When the driver presses the
brakes, the pistons press the brake pads on one side into the rotor, which
causes the caliper to slide over so that the pads on the non-piston side of
the caliper also contact the rotor. Fixed calipers are bolted in place, and
instead have pistons on both sides of the rotor that move when the driver
applies the brakes. Fixed calipers apply brake pressure more evenly and
clamp more firmly on the rotor, however floating calipers are found on most
cars and are perfectly adequate for everyday driving.
5. Sensors:
Some vehicles have brakes that contain sensors embedded in the brake
pads which work to tell the driver when the pads are worn out. Other brake
sensors play a part in the vehicle’s ABS system.
Disc brakes are generally used in passenger cars, but due to their stable
performance at higher speeds and resistance to brake fade, they are
gradually spreading into the commercial vehicle segment, where drum
brakes were traditionally chosen for their longer service life. There are two
types of disc brakes.
The “opposed piston type disc brake” has pistons on both sides of the disc
rotor, while the “floating type disc brake” has a piston on only one side.
Floating caliper type disc brakes are also called sliding pin type disc brakes.
WORKING PRINCIPLE
When the driver steps on the brake pedal, the power is amplified by the
brake booster (servo system) and changed into a hydraulic pressure (oilpressure) by the master cylinder. The pressure reaches the brakes on the
wheels via tubing filled with brake oil (brake fluid). The delivered pressure
pushes the pistons on the brakes of the four wheels. The pistons in turn
press the brake pads, which are friction material, against the brake rotors
which rotate with the wheels. The pads clamp on the rotors from both sides
and decelerate the wheels, thereby slowing down and stopping the vehicle.
disc brake
system
• When brake pedal is pressed, the high-pressure fluid from the master
cylinder pushes the piston outward.
• The piston pushes the brake pad against the rotating disc.
• As the inner brake pad touches rotor, the fluid pressure exerts further
force and the caliper moves inward and pulls the outward brake pad towards
the rotating disc and it touches the disc.
• Now both the brake pads are pushing the rotating disc, a large amount of
friction is generated in between the pads and rotating disc and slows down
the vehicle and finally let it stop.
• When brake pad is released, the piston moves inward, the brake pad away
from the rotating disc. And the vehicle again starts to move.
TYPES OF DISC BRAKES
There are two types of disc brakes. One is called the “opposed piston type
disc brake” which has pistons on both sides of the disc rotor, and the other
is the “floating type disc brake” which has a piston on only one side. The
floating type disc brakes are also called the sliding pin type disc brakes.
1. Opposed Piston Type Disc Brakes

The opposed piston type is a disc brake which has pistons on both sides of
the disc rotors.

The opposed piston type disc brake features stable braking force as well
as a high level of controllability.

The swept areas of the brake pads are enlarged to increase braking force,
and here opposed piston types are favored.

This is because of its advantage where the number of pistons can be
increased to realize even distribution of pressure on the rotors from both
sides. Depending on size of the brake pads, there are several types,
including the 4-pot type which has two pistons on each side for a total of
four, and the 6-pot type which has three pistons on each side for a total of
six.
2. Floating Type Disc Brakes

Floating type is a disc brake which has a piston on only one side, and is
also called the sliding type disc brake.
On the floating type disc brakes, the piston pushes the inner brake pad
against the rotor when the brakes are engaged. This generates a reaction
force that moves the caliper itself along the slide pin, pushing the outer
pad against the rotor to clamp it from both sides.

Many passenger car disc brakes are of the floating caliper type, since this
type has a relatively simple and lightweight construction, which allows for
lower manufacturing costs.

Floating type disc brakes for commercial vehicles

Disc brakes are used mainly for passenger cars, but due to their
consistent performance at higher speeds and resistance to brake fade,
they are gradually spreading into the commercial vehicle segment, where
drum brakes were traditionally chosen for their resistance against wear.
TYPES OF ROTOR
1. Smooth Rotors
Smooth rotors are identified by their flat, smooth surface. For most cars and
trucks on the road, smooth rotors are original equipment (OE) because of
their versatility for many driving conditions. The main benefit of smooth
rotors is that they tend to wear evenly, helping your brake pads last longer.
If you want to keep the smooth rotor but still go for the upgrade, look for
premium metal that absorbs more heat.
2. Drilled or Dimpled Rotors
Drilled rotors are identified by the pattern of holes that have been drilled all
the way through the rotor disc. Dimpled rotors are similar, though instead of
holes there are dimples that have been drilled to the rotor’s minimum
thickness level, retaining more structural integrity than a fully drilled rotor.
These rotor types help the brake pads to better grip the rotor, giving it more
initial bite and increasing stopping power.
*Note that drilled or dimpled rotors are typically found in combination with
slotted rotors.
3. Slotted Rotors
Slotted rotors are recognized by carved lines found on the rotor. These
carved slots help to cool the rotor during high performance use. They also
help to remove dirt and other debris from the disc and brake pad, helping to
maintain consistent contact for more efficient braking. Slotted rotors are
perfect for vehicles that see frequent, heavy towing.
4. Drilled/Dimpled and Slotted Rotors
Rotors that are both drilled (or dimpled) and slotted, while effective, are
best for trucks that want the added aesthetic, such as those with wheels that
have a more open design. Not only will they look great through an open
wheel, but the drilled holes assist with initial bite while the slots are
designed to remove dust and debris from between the rotor and brake pad.
Read more : Types of Brakes | Different types of Braking System
ROTOR MATERIALS
Brake rotors can be made of six different materials, each with its own
advantages. Let’s take a look at each.
1. Cast Iron
This is the very definition of old school when it comes to a brake rotor. It’s
one or two pieces and gets the job done. In fact, it’s the most common
material for brake rotors. The right design (usually two-piece) can even work
well in a performance vehicle. However, it’s also the heaviest option, which
affects the overall weight of your car and its handling, since that weight is
right up there with your front wheels.
2. Steel
Steel has been the racer’s choice for years, because a steel brake rotor is
thinner, weighs less and handles heat better. The downside: Steel rotors
aren’t as durable as some others, and warped rotors can cause noise and a
pulsating pedal when you brake.
3. Layered Steel
Layering sheets of steel together and laminating them makes them resistant
to the warping you might find in a straight steel brake rotor. It’s a favorite of
racers who don’t want frequent brake rotor replacement and repair, but
manufacturers are currently only targeting professional racers and
production is limited, so it’s not terribly common in passenger vehicle
applications.
4. Aluminum
Aluminum brake rotors dissipate heat quickly, but they also melt at a lower
temperature than other options. Aluminum is a favorite for motorcycles,
which weigh less and are easier on the rotors when braking than a heavy
car, truck or SUV.
5. High Carbon
These are iron, but with a lot of carbon mixed in. They can take a lot of heat
and dissipate it quickly. The metallic content helps the rotor avoid cracking
under high stress, and brake noise and vibration are reduced as well. The
only downside is price, which is significantly higher than straight iron or
aluminum.
6. Ceramic
What’s your favorite supercar? Ferrari? Porsche? Lamborghini? Odds are it’s
packing ceramic brake rotors. They offer the highest heat capacity (85
percent higher than cast iron) and superior dissipation, and they maintain a
more consistent force and pressure as the temperature of the rotors rises.
Ceramic is the highest-performance brake rotor available today.
ADVANTAGES AND DISADVANTAGES
Advantages of Disc Brakes
1. It is lighter than drum brakes.
2. It has better cooling ( because the braking surface is directly exposed to
the air)
3. It offers better resistance to fade.
4. It provides uniform pressure distribution
5. Replacement of brake pads are easy.
6. By design they are self-adjusting brakes.
Disadvantages of Disc Brakes
1. It is costlier than drum brakes.
2. Higher pedal pressure is required for stopping the vehicle. This brake
system is installed with vacuum booster.
3. No servo action is present.
4. It is difficult to attach a suitable parking attachment.
More Resources :
Automobile Engineering Parts and System Notes , Article