Brake Before You Break!

October 04, 2018

Brakes are obviously essential components in any motor vehicle. They are used to slow a car down. Without them it would be impossible to stop! For these reasons it’s important to consider how they work. This makes it easier to maintain them and react quickly if there are any malfunctions.


Brake Discs and Drums

Most modern cars will have a separate brake for each wheel. These will be operated by a hydraulic system. The two front wheels will often have braking systems that use discs to compress upon the wheel.  These create enough friction to make the car stop. Drums do not compress the wheel but apply pressure from above in order to create the same result.

Most modern cars are installed with discs because they last a lot longer and slow down a car more safely. When braking harshly on drum brakes, there is a much higher risk of whiplash.

The reason why it’s most important to have disc brakes on the front wheels is because this is where most of the force is placed when stopping. When the brakes are slammed, all the force of momentum is shifted to the front of the car. That is why it is essential to have quality brake discs.


Hydraulic Braking Systems

In hydraulic braking systems there are master and slave cylinders connected by valves. The cylinders are filled with brake fluid. When a brake pedal is pushed, pistons in the master cylinder pump the brake fluids through the valves. This transports the fluid to the slave cylinders. Each wheel will have a slave cylinder and pushing the brakes will result in all cylinders being filled with brake fluid in this way.

This system ensures that the same amount of fluid is distributed to every wheel. Therefore, the combined force of all the slave pistons is greater than that of the master cylinder.  In such a way, the master piston moves a relatively long distance (a few inches) to make the slave pistons move the tiny margin needed to apply the brakes effectively.

The combined hydraulic system allows huge amounts of force to be exerted on the brakes in this way.  In many ways, it is like the pivotal system present in objects like cranes where a long-handled lever is able to lift extremely heavy objects. 

Modern cars will often have twin hydraulic circuits. These have two master cylinders which work in unison. Even if one fails, the system can still operate effectively.

Depending on the make of car, circuits can be used to control all the brakes or there can be separate circuits to control each brake individually.

On occasions where it is necessary to brake heavily, almost all the force is released from the rear wheels and hurled towards the front of the car. Therefore, the rear brakes can cause the wheels to lock suddenly and the car will be sent into an uncontrollable skid. This is why the brakes on front wheels are deliberately more powerful than those on back wheels. It is an attempt to balance the effect of all force being thrown to the front of the car.


New cars load sensitive brake system:

All new cars will also have a load-sensitive system that can tell how much weight is onboard. This will limit the amount of pressure on the brakes accordingly in order to prevent uncontrollable skidding.

The most advanced braking systems will even be able to sense the nature of deceleration being caused by braking and make sure that exactly the right amount of pressure is applied to prevent dangerous skids. The brakes will release and apply themselves in very quick succession to make sure that the car slows down appropriately without the wheels locking.

Power Assisted Brakes:


Modern cars will often also have power assistance in order to minimize the amount of human effort needed to apply the brakes effectively.  The power is created by using the difference in air pressure between the vacuum of the inlet manifold and the atmospheric air around it.  The servo is connected through pipes and is fitted between the brake pedal and master cylinder. This means that a driver is able to apply the brakes heavily without needing too much strength in their legs.  This certainly makes driving safer for those unable to apply a great deal of pressure with the strength of their legs alone.