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The Ultimate Guide To Car Brakes (Parts, Function, Fixes, FAQs)

December 20, 2021

Here’s something to think about the next time you’re driving:
Moving at 60 mph, a car needs approximately the length of a football field to stop completely.

Imagine how much longer it’d take if your brakes weren’t in prime condition?
With that said, what makes up a vehicle brake system

Cars have more than one way to brake — typically hydraulic brakes, engine braking, and parking brakes

However, in this article, we’ll be tackling the hydraulic brake system, the one most people think of when talking about brakes. 

We’ll explore its parts, problems associated with them, and cover some brake FAQs.

This Article Contains:

Let’s dive right in!

What Do Car Brakes Do?

Vehicle brakes use leverage, hydraulic force, and friction to stop your car. 

Leverage happens when you press the brake pedal. This actuates the master cylinder, which delivers hydraulic pressure to the braking mechanism at the wheels. 

Friction applied at the wheels converts kinetic energy (from the wheel’s motion) to heat, which dissipates into the air gradually. This is why your brakes get hot

Fun fact: Brake pads can reach temperatures over 950oF!

But brakes aren’t just a bunch of discs at your wheels. 
There are tons of brake parts that are interconnected. 

Let’s see what these parts are and how they relate.

What Are The Components Of A Brake System?

We’ll go through the primary parts of a car braking system, as each one triggers the next:

1. Brake Pedal: Creates Leverage

The brake pedal is usually the pedal on the left side (of a 2-pedal automatic car) or the middle pedal (of a 3-pedal manual car). 

Hydraulic braking begins when you press the brake pedal, triggering a sequence of events that lead to action at the wheels. The brake light switch is also connected to the brake pedal, so pressing it turns on the brake lights. 

While the brake pedal rarely causes issues on its own, it often reflects problems in the braking system. 

Here are some examples: 

2. Brake Booster: Amplifies Your Foot Power

Braking takes a lot of force. 
Think about it — you’re using just one foot to stop a 2-ton vehicle. That’s where the brake booster comes in. 

This ingenious device amplifies your foot power from the brake pedal. It does so using the vacuum from the intake manifold and differences in air pressure, resulting in much more force punching into the master cylinder.

If you have a bad brake booster:

3. Master Cylinder: Converts Force To Hydraulic Pressure

The master cylinder converts kinetic energy from the brake booster into hydraulic pressure.  

Here’s what happens:
Brake fluid fills the master cylinder (from the brake fluid reservoir). 
Force from the brake booster pushes the master cylinder piston that “compresses” the brake fluid through the brake lines. 

As liquid isn’t actually compressible, pressure builds and is communicated to the braking mechanism at the wheels. 

The master cylinder usually has 2 cylinders (a tandem design) controlling 2 separate hydraulic circuits — each handling 2 of your 4 wheels. This is a safety measure in case one hydraulic circuit fails.

If the master cylinder fails, here’s what can happen:

4. Brake Lines And Brake Hoses: Transfers Hydraulic Pressure

Brake lines and brake hoses form conduits from the master cylinder to the braking mechanism at the wheels. They carry brake fluid and communicate hydraulic pressure to your disc brakes or drum brakes.

So, how are a brake line and brake hose different?

A brake line is a rigid metal tubing running along the chassis.
A brake hose is a flexible tubing connecting the rigid brake line to the braking mechanism,  where there’s wheel movement. 

Damage to brake lines or brake hoses typically results in:

5. Disc Brakes: Creates Friction By Squeezing

A disc brake has a caliper, brake pads, and brake rotor.

When the brake pedal is depressed, pressure through the brake fluid engages the caliper pistons, causing the brake pads to squeeze the spinning rotor. Friction between the brake pads and rotor stops the wheel. 

6. Drum Brakes: Creates Friction By Pushing

A drum brake comprises a brake drum that encloses a wheel cylinder and brake shoes

When you engage the brake pedal, brake fluid pressure actuates the wheel cylinder, which pushes a pair of brake shoes apart and onto the insides of the spinning brake drum. Friction between the brake shoes and drum halts the tires.

You now know the basic chain of reaction from the brake pedal to the disc (or drum) brakes. 
Let’s focus on the braking mechanisms, starting with disk brakes. 

Understanding Disc Brakes

Disc brakes have an open design, allowing them to dissipate heat efficiently. You’ll find them on all 4 wheels of your vehicle, or at least on the front 2 wheels when in a disc/drum brake combo. 

Front wheels take up around 75% of the braking force. Disc brakes are preferably mounted on front wheels because they can handle more heat and have a faster braking response compared to drum brakes.

Here are the primary parts of a disk brake:

1. Brake Rotor (Brake Disc): Spins With The Tires

The brake rotor (or brake disc) is mounted to the wheel and spins with it.

Brake rotors are typically steel, cast iron, or carbon-ceramic and have different drilled or slotted designs to help with heat dissipation. 

Over time, the rotor surface will wear down from contact with brake pads. As its thickness is a significant performance and safety factor, always consider changing the rotor during a routine brake pad change.

Here are some issues associated with damaged rotors: 

2. Brake Caliper: Squeezes Brake Pads Onto Rotor 

The brake caliper is mounted over the brake rotor, has pistons, and holds brake pads on either side of the rotor.  Brake calipers are typically one of two designs — a floating caliper (pistons on one side) or a fixed caliper (pistons on both sides).

Faulty brake calipers can manifest these situations:

3. Brake Pads: Stops The Rotor

Brake pads are mounted on the brake calipers, with their friction material facing the rotor. They come in different materials that offer varying levels of stopping power, longevity, and brake dust generation. 

As the friction material wears down with use, worn pads shouldn’t be less than ¼ inch thick before you get new brake pads.

And here’s some of what happens with worn brake pads:

Next, let’s take a closer look at drum brakes.

Understanding Drum Brakes 

Drum brakes are an older brake type with an enclosed design. 

They’re more complex than disc brakes but cheaper to replace, and it’s also easier to install parking brakes in them. So, you’ll still find them on economy models or as rear brakes where less braking force is needed. 

Because they’re a closed configuration, they overheat faster than disc brakes and have more tendency to experience brake fade.

Here’re the main pieces of drum brakes:

1. Brake Drum: Rotates With The Wheel

The brake drum is affixed to the wheel hub and rotates with it. It’s typically made of iron, making it quite resistant to wear.

Here are some issues that occur with brake drums: 

2. Wheel Cylinder: Pushes The Brake Shoes Onto Brake Drum

The wheel cylinder is located inside the brake drum, mounted to the top of the backing plate. It usually has 2 pistons attached to brake shoes and pushes them outwards in response to braking pressure.

Here are some issues related to a faulty wheel cylinder:

3. Brake Shoes: Stops The Brake Drum

Brake shoes are curved metal pieces with a friction lining on one side. They’re mounted inside the brake drum, with the friction material facing outwards, towards the brake drum’s inner surface. Like brake pads, brake shoes come in a variety of material options too.

When you have worn brake shoes, this can happen:

We’ve gone through primary brake components. 
Next are some indicators that you need a brake inspection. 

5 Signs You May Need A Brake Job

If you’ve been following carefully, you’ll notice that bad brake symptoms can be similar for different braking system issues. 

Here’s a lineup of the 5 usual suspects, and sometimes they come together:

1. Odd Sounds

A high pitch squealing often means worn brake pads that demand replacing. This is one of the more common issues. 

On the other hand, grinding, rattling noises may indicate anything from damaged brake pads dragging painfully against a rotor, to broken brake pieces rolling in a brake drum. Could even be a wheel cylinder piston that fell out of its bore. 

Now that’s really bad news as you’ll be leaking brake fluid and losing hydraulic pressure. 

2. Irregular Pedal Behavior

Take note whenever your brake pedal acts differently than usual. 

A soft, mushy pedal or one that sinks to the floor can mean anything from a brake fluid leak, air bubbles in the brake line, to worn pads.

However, a hard, stiff pedal or one that rides high may indicate brake booster issues or extreme brake fluid contamination.

3. Pulling To One Side

If your car feels like it drifts to one side, it can be from a stuck caliper or wheel cylinder piston, collapsed brake hose, or unevenly worn brake pads. 

However, drifting might not even be a brake problem. It could be caused by unevenly inflated tires (possibly a punctured tire) or poor wheel alignment.  

4. Vibrations

Vibrations often come from warped rotors as uneven surfaces thrum against the brake pads. However, misaligned wheels can cause it too. 

You may also experience this if doing an emergency stop with ABS brakes — which isn’t a brake problem. It’s just the ABS making quick grabs on the rotor to stop the car safely.

5. Brake Warning Light Flashes

A lit brake warning light covers a series of errors, from low brake fluid levels, ABS issues to a still-engaged parking brake. Don’t ignore this light if it pops on.

If your vehicle displays these signs, you should get a brake service ASAP. Your road safety is certainly worth much more than a brake repair or new brakes. 

Now, let’s move on to some FAQs on brakes. 

4 FAQs On Brakes

Here are the answers to more brake topics:

1. What Are Some Common Brake Terms?

These are some common terms you might encounter when looking up brakes:

2. What Is The Parking Brake?

The parking brake system is a completely separate device that bypasses the hydraulic brakes. It typically employs the rear brakes and uses only cables and levers to work. 

The parking brake keeps your car stationary, so it doesn’t move or roll off a slope. It’s also called an emergency brake because it can stop the tires if hydraulic brakes fail —  just never do this at speed.

3. What Are ABS Brakes?

The Anti-Lock Braking System (ABS) is an add-on to the regular braking system. It’s designed to prevent wheels from locking during heavy braking, to avoid vehicle skidding or hydroplaning. ABS allows for safer, faster, controlled stops.

4. How Much Does It Usually Cost To Replace Brakes? 

Replacing “brakes” typically refers to replacing your brake pads or shoes. The cost for new brakes varies based on vehicle make and model, location, and friction material used. 

However, it can be between $150-300 per axle on average. Just keep in mind that a brake repair can involve more than just replacing brake parts.

Closing Thoughts

Good driving practices include gauging sufficient braking distance, avoiding tailgating (to prevent emergency brakes), and applying gentle pressure on your brakes. Minimizing rash brake use can help improve fuel economy and prevent unnecessary wear to brake components. 

Also, remember that periodic brake inspection and regular brake service can help you plan brake repairs and spread out the cost. 

And if you ever need a simple solution to brake repair, you can always count on RepairSmith!

RepairSmith is a mobile vehicle repair and maintenance service, available seven days a week. Contact us for help, and our ASE-certified mechanics will drop by and get your car’s brakes fixed ASAP.