Can you imagine a car or a bike without a braking system? Without a brake system, it’s difficult to control the vehicle. The brake system is an essential safety system of the vehicle. In this blog, you will learn about the functions of the automotive braking system and types of braking systems.
Content: Brake System
Types of braking system
Mechanical brake system
Hydraulic brake system
Difference between drum brake and disc brake
Key components of a hydraulic system
Working principle of a hydraulic brake system.
Key components of a hydraulic system
Key design parameters of the braking system
Hydraulic braking system – Functional requirement
Air Brake
This blog is about the automotive braking system. Let’s understand the types of automotive braking systems.
Types of brake system
1.Mechanical brake system
2.Hydraulic brake system
3.Air brake system
Mechanical brake system
Mechanical brake system commonly used in motorbike and bicycle. The mechanical brake system is suitable for a lightweight vehicle. The mechanical brake system is not efficient to control the speed of a car or heavy commercial vehicle. It works well to control a single wheel. It’s complicated to apply the brake on multiple wheels by the mechanical brake system.
Now modern bikes are equipped with a disc brake that operates on a hydraulic system.
Drum brakes operate by mechanical brakes system. he mechanical brake system operates by lever and cables.
The mechanical brake system operates by lever and cables. In a mechanical brake system, leavers are subjected to joint relaxation, so after every 400 to 500 kilometres brake pedal play and brake adjustment essential.
Hydraulic brake system
Hydraulic brake systems are more efficient to control vehicles compared to a mechanical brake system. Hydraulic brake system further categorized as,
Drum brake
Disk brake
Difference between drum brake and disc brake
| Drum Brake | Disc Brake |
| Construction: Consist of brake shoes and drum. The drum is a rotating element and brake shoes are stationary. | Construction: Brake caliper assembly, brake pad & disc. The disc is a rotating element and the brake caliper (brake pad) is a stationary component. |
| Working Principle: Brake is actuated brake shoes are expanded and apply pressure on the inner circumference of the drum which stops the drum (wheel). The radial force is applied to the drum. | Working Principle: Once the brake pedal/lever (of front disc brake in the bike) is applied, brake pad actuates and moves in the axial direction of the disc and applies pressure (frictional force) on the disc. This action reduces disc rotational speed and applies the brake. |
| Material: Brake shoes are made from frictional material and the drum is made from cast iron | Material: Disc caliper is made from cast iron, disc pad is nothing but frictional material, and the disc is made from steel. |
| Cons: Bulky in design and more prone to brake fade. | Pros: Compact design. Less prone to brake fade as better heat dissipation is possible. Better control as compared to drum brake. |
| Pros: Less expensive as compared to disc brake. Drum brakes can be operated by a mechanical lever system. | Cons: Expensive as compared to drum brake. Cannot be operated by lever or wire, a hydraulic system is required. |
Please do watch the following interesting video about the 2 disc system (360 mm disc). Of course, it’s not a real disc brake, it’s one of the trending videos of bike alteration.
The difference between the drum brake in the hydraulic system and the mechanical brake system is the actuation of brake shoes. In a hydraulic brake system, brake shoes are operated by the brake cylinder.
Working principle of a hydraulic brake system
Please review the following animation carefully to understand the working principle of a hydraulic brake system.
Key components of a hydraulic system
| Main Components | Sub-components |
| Master cylinder Assembly | Brake fluid reservoir, brake pedal, master cylinder, brake vacuum assist |
| Hydraulic Pipeline | Hydraulic pipe, hose |
| Brake caliper assembly | Brake cylinder, brake shoe (in drum brake), brake pad (in disc brake). |
The Master cylinder assembly consists of a brake fluid reservoir, brake pedal, spring-loaded piston. The brake pedal actuation pushes the master cylinder piston. Movement of the master cylinder spool/piston inside a brake master cylinder closes the fluid inlet port. The closing of the fluid reservoir’s inlet port generates a closed-loop system in the brake circuit. The brake fluid inside the brake system pushed by the master cylinder piston will generate a hydraulic force (as fluid cannot be compressed) in the entire system.
Once the brake pedal is released, it pulls out the master cylinder piston rod (as the master cylinder piston rod is mechanically connected to the brake pedal lever). The compression spring inside the master cylinder also maintains a leak-proof system between the inlet port and compensating port.
Once the master cylinder piston reaches a normal position, the inlet port of the brake fluid reservoir opens, which lowers the pressure inside the brake system.
The wheel cylinder piston also reaches a normal position which maintains a clearance between the disc/drum and brake pad/shoe.
Key design parameters of the braking system
- More force is applied by the brake caliper piston as the surface area of the master cylinder piston is less than the brake caliper piston.
- The longitudinal movement of the master cylinder piston is greater than the brake caliper piston.
The hydraulic jack also operates on the same principle, a small piston lifts the entire car.
Hydraulic braking system – Functional requirement
- Leak-proof design – Reliable braking system.
- The hydraulic fluid must withstand high operating temperatures inside the engine compartment and work well in below zero degrees centigrade atmospheric temperature.
- The Brake system should operate in wet and dry conditions.
- The Brake system should be designed in a split service brake system. In case one hydraulic circuit fails, secondary circuits still need to work.
- The heat generated due to friction between the brake pad/shoe and disc/drum must be to avoid brake fade.
Please do watch the following YouTube video about Design – FMEA of the braking system.
Never adjust brake pedal play. All modern vehicles are equipped with a brake assist system.
This is adjustment must be done at authorized service providers.
If you feel excessive brake pedal play than normal it could be an issue with low brake fluid inside the brake system.
Air Brake
Air brake is most commonly used in heavy commercial vehicles. (trucks and buses). Air brake operates on compressed air, it’s also known as a compressed air brake system. The air brake system consists of the following components,
- Air filter
- Air compressor (driven by engine crankshaft)
- Air dryer and cooling unit
- Safety valve & pressure regulator
- Air tank/reservoir
- Hose and pipe
- Brake actuator (air cylinder)
- Levers to operate brake shoe
- Air brake system pressure and air leakage indicator
- Parking brake system
Air brakes are most suitable for multi-axle vehicles and where trailer wheel brake system to be coupled with the truck carrier.
Please watch the following animation about heavy truck brake function
Hydraulic brake Vs. Air Brake
| Hydraulic Brake System | Air Brake System |
| The hydraulic brake is more suitable for lightweight vehicles. | Air brakes most suitable for heavy vehicles like buses/trucks. |
| The hydraulic brake system is not suitable for heavy vehicles. | Air brake application on light vehicle become bulky and complicated so it’s not used in the light vehicles. |
| Lower maintenance cost as compared to air brake. | Higher maintenance cost. |
| Fewer system components as compared to air brake, hence the lower cost. | A complex & costly braking system as it involves multiple components like an air compressor, air tank, filter, pressure regulators. |
| Hydraulic brakes are easy to operate. | Air brake operation needs special skills. An operator must ensure proper air level in the reservoir before transportation. |
| The hydraulic brake system fails if small leakage existing in the system. Small leakage drains out brake fluid completely from the system. | The air brake system still can be operated with leakage as compressed air supply is always maintained. |
| Better fuel efficiency as there is no need for a fluid pump to operate the brake system. | Crankshaft drives air-compressor. Lower fuel efficiency as the air compressor needs to be operated with the engine for a constant supply of compressed air to the reservoir. |
Brake system troubleshooting and safety tips
Master Cylinder failure
- Failure of master cylinder piston seal (made from rubber) – Rubber seal maintains a leakage-proof system inside the hydraulic system, failure of rubber seal or worn out rubber seal won’t be able to maintain closed-loop (positive fluid pressure) within brake circuit. This leads to a reduced braking effect or complete failure of the system.
- Impurities / contaminated brake fluid: Impurities/dirt inside brake master cylinder seriously damage brake master cylinder piston seal. Contaminated brake fluid reacts with rubber parts which eventually reduce seal life (rubber seals are subjected to shelf life).
- Incorrect brake fluid selection: Incorrect brake fluid types use in the braking system leads to a serious failure of the brake master cylinder seal and ABS (Anti-lock brake) system). Use the only recommended brake fluid. Eg. If Chevy Cruze owners manual specifies DOT 3 & DOT 4 brake fluid, use only recommended and branded brake fluid.
What is brake fade?
It’s a phenomenon of reduced brake power or temporary loss of brake system due to increased temperature of brake shoe/brake pad during high speed or high load working conditions. As compared to a disk brake, the drum brake is more sensitive to brake fade.
Heat dissipation in disc brake is faster as airflow is directed towards the disc caliper and disc-equipped with internal vanes or holes for heat dissipation. However, failure of the slave cylinder (braking pad sticking issue) can cause brake fade issues in the disc brake system too.
Please watch the following animation about the brake fade issue in the disc brake.
Brake Pedal free play Adjustment
Typically free play is provided in brake pad and master cylinder piston spool by the automotive manufacturer. It’s normal to have a free play between 1 mm to 10 mm (it differs in each car model and make). The Master cylinder piston spool is (compression) spring-loaded, this ensures an open-loop system in the braking system circuit. Whereas brake pedal is also equipped with spiral spring or tensile spring (depends on vehicle manufacturer). Brake pedal free play is essential to avoid the transfer of vibration of the brake pedal on the master brake cylinder spool.
Why is my brake sticking?
Brake sticking is nothing but brake still in engaged condition even you release the brake pedal.
Another reason for brake sticking is due to faulty wheel cylinder (I did face this issue) Worn out wheel cylinder piston will not retract the brake pad which leads the brake pad will remain in contact with the disc.
Downshift while braking?
It’s perfectly fine downshifting gear while braking,
- It will help to control the vehicle quickly. With lesser distance vehicle can be controlled
- It will also reduce the chances of brake fade as downshifting of gear generates a braking effect by the engine itself.
- Long life of brake pad/brake shoe.
- it will help to quickly accelerate as downshifting generates more torque
Tips – Downshift while braking?
Do not press clutch continuously while downshifting. The clutch pressing cut of the engine connection with the wheel. This leads to more load on the braking system.
Downshift like this way 5-4-3-2 if required 1st gear
Remember always prefer to drive in a lower gear when you are descending the ghat (steep hill) . Driving in ghat (while descending steep hill) with continuous brake application will generate more heat and which further leads to brake fade (loss of braking effect). If you are descending ghat at 40 Km per hour, try to apply brakes as minimum as you can. Instead of brake drive vehicle at 3rd gear without pressing the clutch (which generates an engine braking effect while descending ghat.)
Wet brake Vs Dry Brake
The difference between a wet brake and a dry break it’s operating condition. Wet brakes submerged in transmission oil. Transmission oil dissipates heat from the brake disc whereas dry brakes heat is dissipated by air flowing over disc caliper and disc.
Wet brakes runs cooler than the dry brake. Wet brakes are enclosed in the axle.
Wet brakes widely used in tractor as tractor used in mud paddy. Dry brakes will not work in paddy/mud.
We hope, this blog was helpful to understand the automotive braking system.
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What are the three braking systems?
1. Mechanical – Mostly used in motorbikes (less than 150 cc engine) & bicycles.
2. Hydraulic- Used in light commercial vehicles, SUV, MUV, and cars
3. Air Brake – This brake system is used in heavy vehicles eg. Trucks, buses, railway
What are the types of braking system?
1. Mechanical Braking System: Drum brake. Suitable for motorbikes.
2. Hydraulic Braking System: Drum brake or disc brake
3. Airbrake System: In the airbrake system, mostly drum brake is used. Suitable for heavy vehicles.
4. Anti-lock Braking System (ABS): This is a safety feature equipped with an existing hydraulic braking system.
5. Electromagnetic braking system: This brake system is suitable for parking brakes in the car and is also used in industrial machines