There are many different types of braking systems that have been used over the years. In this section I’ll describe the different types, how they operate, and how these systems have evolved over time. Learn which types are commonly used in today’s vehicles.
How They Work
Brakes work on the principle of hydraulics. When you apply pressure to the brake pedal, this braking force will multiply based on the piston diameter at the master cylinder at each corner or wheel of the car. This is how you are able to stop a 3000 pound vehicle with a small amount of force from your foot.
Side note about Hydraulics
At Sci-Culture.com you can learn about how force, area, and pressure work with hydraulics in an automotive braking system.
Parts of the typical Non-ABS Brake System
Start with your foot and move through the system to get familiar with each component and what its purpose is. Here is an animated illustration of a non-ABS brake system to help you visualize and learn where these parts are located in and around a vehicle..
The Brake pedal is where you apply pressure in order to stop the vehicle. (The mechanical advantage)
The pressure is applied to a component called the master cylinder. With the brake pedal mounted in the pedal cluster assembly…
The pedal arm has a pivot point for forward and backwards movement. This pushes a metal rod from the inside of the vehicle through the fire wall and brake booster into the master cylinder. These components are located in the engine compartment area.
The master cylinder is the main fluid control area where the pressure that is applied is distributed to each part on the vehicle. (The hydraulic advantage)
The master cylinder has two chambers inside it where small pistons and seals push the fluid in two directions, to the front and to the rear. Here are 2 plugs in this new master cylinder, one is for the front fluid distribution and the other is for rear.
This Auto Zone brake fluid is a special fluid that is used only in the brake systems and is not meant for any other system in your car.
Brake fluid has a synthetic base with a very high temperature/heat range. These two things allow protection from moisture in the system and to keep the fluid from boiling, considering the extreme temperatures that are generated from the friction between the brake pads and rotors when stopping your car. Note: most brake fluids have a boiling point of 450°F. (Fahrenheit)
Power Brake Booster
Even though brakes are hydraulically operated and perform using a great deal of pressure to stop vehicles with a large amount of weight, power brake boosters offer an assist which eases the amount of force need to stop the vehicle.
There are two types of power brake boosters used on vehicles today, vacuum and hydraulic assist.
Engines naturally produce a vacuum that can be harnessed and used to provide an extra amount of force to the master cylinder when applying the brakes.
Here is a master cylinder and brake booster together. Notice the vacuum supply hose from the engine, it has a one way check valve (white) to keep vacuum stored after the vehicle is shut off. This allows vacuum to be readily available to use for the power assist on the next start up.
Hydraulic assist works off a two chambered belt driven pump. Mounted and driven off of the engine, the one chamber operates the power steering to ease the turning effort and the other operates the power assist for braking effort.
“Hydraulic Booster Photo”
The next component in line is the combination valve. With brakes applied, the pressure now travels through this valve sending the fluid to each corner of the car. The main purpose is to divide the front brakes from rear. This is to prevent total brake failure if there is a pressure loss on one axle. You’ll still have brakes on the one remaining axle. The valve also has a sensor which signals a warning light if a pressure problem occurs.
Combination valves are an early pressure control design. Once vehicles started using anti-lock brake systems (ABS) they incorporated the pressure control into a hydraulic pump. The pump is controlled by an electronic brake control module.
(More on ABS in Automotive Brakes-Part 2)
The fluid now travels through brake lines approximately 3/16 of an inch in diameter. The fluid is being sent to each corner of the car to a specific type of brake assembly that helps to stop the car.
There are two types of brake designs. They are drum and disc style braking systems.
There are 3 main parts to this type of brake assembly. These 3 parts are:
The fluid comes into the drum type brakes to a component called a wheel cylinder.
This cylinder is where the hydraulic pressure is pushed to. Similar to the master cylinder, the wheel cylinder has one chamber with two pistons and seals.
Within the brake assembly, there are two brake shoes that have a special fiber and metallic substance to help aid in the stopping of the vehicle.
The pressure in the wheel cylinder forces out the shoes which are mounted to a flat backing plate by springs and lock pins.
The pins keep the shoes mounted against the backing plate while the springs allow the shoes to move in and out within the drum assembly.
When the brakes are applied
The shoes contact the inner surface of the drum and slowly stop the vehicle. When the brakes are released, the springs pull the shoes away from the drums allowing the brakes to disengage.
Drum Brake Application
See an animated drum brake system hydraulics illustration.
There are 3 main parts to this type of brake assembly also. These 3 parts are:
Floating Brake Caliper
The brake fluid comes into the disc brake assembly to the caliper. The caliper is a c-shaped housing with one or more pistons in it. The floating caliper design refers to how its mounted above the rotor, slides on 2 pins, and floats back and forth when the brakes are applied. The most common design is a single piston caliper. Other types are dual piston and four piston calipers.
The brake pads are made up of a special fiber and metallic material that helps to stop the vehicle while still having a long life span. Brake pads are commonly referred to as semi-metallic. The softer fiber material helps to dissipate heat while the metallic chips give it strength. There is a smaller amount of metal so that they don’t retain as much heat. These two materials bond together to form the brake pad.
Brake Pad Sensors
Brake pads have 2 types of wear indicators. The most common type has a thin metal tab mounted on it with a pre-determined depth that contacts the rotor surface and makes a squealing noise to alert you before they are completely worn out. The other type is a sensor that cuts through or contacts the rotor surface grounding out a warning light in the instrument cluster to get your attention when worn.
When the brakes are applied, the pistons within the caliper housing squeeze the brake pads against the brake rotor slowing the vehicle to a stop.
Disc Brake Application
See an animated disc brake system hydraulics illustration.
Just as any type of automotive system has evolved over the years the brakes, although similar in nature have been designed and re-designed again and again. These changes evolve into more modern and updated designs that work better and are safer for today’s vehicles.
The two types of disc brakes that are commonly used are vented and non-vented.
Vented rotors are used on all front brake assemblies and some rear brakes of today’s vehicles to help bring in air that will cool off the rotors when they heat up. Due to the amount of braking force needed and weight transfer that is applied to the front rotors, the friction builds heat and the heat creates two problems. Problem 1; heat warps rotors. Problem 2; excessive heat can put stress on the brake fluid (especially if its old fluid) and when it reaches it’s boiling point it creates brake fade. Brake fade is a condition where the pedal drops or fades toward the floor when holding pressure or trying to stop. This is why it’s important to keep your brakes cool.
Here is an end view that shows the rotor vanes for cooling down the temperature and to prevent warping and fading. Depending on how severe the rotors may be warped, they can be machined on a lathe. If they fall below a minimum thickness specification they will need to be replaced. A majority of manufactures make rotors at or just above the minimum specifications and machining or resurfacing would be out of the question. Resurfaced rotors tend to warp a little bit faster than new rotors due to the smaller amount of material remaining on the rotor.
Non-vented rotors are used on rear brakes. There is less friction and heat generated from rear brakes so the extra cooling is not needed.
All manufactures have used both types of braking systems and a variety of combinations and mixing the two systems.
(Drum front and rear, drum rear and disc front, front and rear disc, and rear vented or non-vented)
This is the basics of how the hydraulic brakes work, but not the end.
The emergency brake or hand brake operates using the same components in the hydraulic system, with one exception. There is a mechanical advantage or over ride built within these systems.
Generally speaking, the Emergency brake is considered a secondary braking system. If the primary system fails in any way you have a back up system to help stop the vehicle and prevent an accident from happening.
When applying the emergency brake in a drum brake system
The cable pulls a lever within the brake shoes to push them into the drum allowing the vehicle to stop.
There are two types of rear disc emergency brake set ups. If you have rear disc brakes, one type has the cable pull a lever.
Disc caliper E-brake photo
The lever pulls a ratcheting mechanism inside the caliper housing under the piston. This operation squeezes the pads without using hydraulic pressure.
The other type has an internal drum within the rotor that operates like standard drum brakes.
Rotor/drum E-brake photo
The cable pulls the shoes into the drum without hydraulic operation. The importance in this is that if there is a sudden loss in brake pressure you can use the “emergency brake” to mechanically apply the rear brakes and bring your car to a stop safely.
Use the key terms list below to refresh your memory about Brakes 101 and proceed to the brake quiz to test your knowledge.
Key Brake Terms
Emergency brake cable
(Key terms in bold through this post)
Now that you completed the Brakes 101 – part 1 section, test your knowledge with a brake quiz to see what you’ve learned.
Now that your through with Automotive Brakes 101-Part 1, you can refer back to System 101 for more automotive topics
Automotive Brakes 101-Part 2 (ABS functions)
Automotive Brakes 101-Part 3 (Performance upgrades)
Automotive Brakes 101-Part 4 (Electrical-ABS fault tracing)
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