Disc Brake: The Ultimate Guide

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If your car is a recent make and model, it will likely have disc brake instead of drum brakes. That is because these are the most used brake types in the modern car. Disc brake offer better performance in many ways. But then, you can only feel these benefits if you understand how this disc brake work and ways to maintain them. That is why up together this guide- to help you understand your car brakes better so you can take care of them.

Here, you will learn about the disc brake system from the different types, working, to the problems that could be making these brakes to fail. You will also get to know how to fix these problems yourself. And if you take your car to a mechanic, the repair steps the mechanic will or should take. You will also learn about the useful tip to maintain a disc brake system for your safety and that of others.

Read on and equip yourself with useful knowledge about this essential part of the modern automobile.

What Is A Disk Brake?

As the name indicates, a disc brake is the brake type that uses a disc for the frictional surface. This is the surface that is contacted by the pads when brakes are applied.  A disc brake system is often contrasted with a drum brake, a type that uses drums in the place of discs.

Disc brakes have become the standard types of brakes today, with virtually every car model and make today using them. These range from race cars, trucks, to the usual passenger vehicles. Various disc brake advantages make these types of brakes a popular option as we will see in a while.

Disc brakes are not used in cars only. You will also find them in bikes, both motorized and non-motorised. The disc brakes used in cars and the disc brake bike version are almost similar with difference mostly in the design. Let us now look at the working of disc brakes – the mechanism they use to stop a moving automobile.

Diagram that shows how disk brake works
Source: http://www.lesschwab.com

Disc Brake Working Principle

These brakes are usually hydraulic, so all our references are to this type a braking system. A disc brake comprises different parts that work together to transmit as well as amplify the force of the foot on the brake. This is what happens.

When you step on the brake pedal, a push rod pushes and applies pressure to the master cylinder piston. This causes brake fluid to move out of the master cylinder to the brake lines or tubes that go to the brake caliper.

These hoses are connected to the pistons in the caliper, so they carry the fluid pressure from the master cylinder to the caliper pistons. The pistons slide from their bores as a result of the fluid pressure. This movement pushes the brake pads toward the rotor- the disc that rotates together with the wheels.

Depending on the amount of force at the brake pedal and its duration, the brake pads will contact the brake rotor to either reduce its speed or stop it from spinning. Releasing the brake pedal allows a return mechanism for the parts involved, and the brake fluid returns to the master cylinder ready for another braking action.

Here is a disc brake diagram that shows the different parts involved when braking.

Types Of Brake Discs

Disc brakes come in two types: opposed piston and floating. These names are derived from the type of brake caliper used. The opposed piston disc brakes use calipers that have pistons on either side of the rotor while the floating types employ calipers with pistons on one side only. These brakes are also known as the sliding pin disc brakes.

Opposed Piston Disk Brake Sample Image
Source: http://www.performanceonline.com

  1. Opposed piston disc brakes- due to the presence of pistons on both sides, these brakes provide a braking force that is more stable. They also offer the driver better control of the braking system. Because the frictional surface that is contacted by the loads is large, these types of brake discs create higher vehicle stoppage forces and are the most suitable in heavy duty applications.

The number of pistons in these disc brake types can also be increased to match the braking power required. That is why some high-performance vehicles will have these brakes featuring as many as six pistons.

Source : http://ssbrakes.co

  1. Floating disc brakes- as we have seen, these brakes have calipers with pistons only on one side. The number of pistons can be one or two. The piston function is to push the brake pad to squeeze the inner side of the brake rotor. This causes the floating caliper to move on its slide pin, working a mechanism that pushes the pad on the other side of the caliper.

These types of disc brake are common in passenger cars where high braking power is not necessary. Also, where lightweight calipers are required. Floating disc brakes also cost less to manufacture, which makes them low-priced on the market.

Differentiate Drum Brakes and Disk Brakes
Source: http://www.youtube.com

Disc Brakes Vs. Drum Brakes

Disc brakes have, in recent years, become the most preferred types of brakes. But why? The are many reasons for that. Let us now look at the advantages of disc brakes when compared to drum brakes. We will also look at the disadvantage. For clarity, we summarized the benefits and drawbacks into point form.

Disc Brake Advantages And Downside

Disc Brake Advantages

  • Less effort to stop a speeding vehicle- compared to drum brakes, disc brakes don’t need a lot of force. This is due to the design and construction of the disc brake system and one of the reasons for their use in race cars and trucks.
  • Faster cooling- the function of brakes is to convert the kinetic energy of a moving vehicle into heat energy that can then dissipate into the air. A lot of heat is, therefore, produced. Disc brakes disperse this heat better due to the disc design.
  • Less heat generated- when subjected to the same braking force and conditions, disc brakes produce less heat than drum brakes.
  • Better performance in wet conditions- disc brakes remove water more efficiently, especially if the rotor is the slotted or drilled type. This makes them maintain braking power even in wet environments without the skidding that is common with drum brakes.
  • Pad wear indicators- disc brakes come with a pad wear indicator. You don’t find that in a drum brake.
  • Easy to maintain- disc brakes are easily accessible and maintaining them is easy. In most cars, you can even check the condition of the frictional surface without having to remove the wheel.

Disc Brake Downsides

Disc brakes are not without disadvantages which include:

  • Cost- disc brakes systems are more expensive when compared to the drum brakes.
  • Complexity- these brake types have more parts. This makes them complex systems. In the event of failure, they can cost more to troubleshoot and fix.

Overall, disc brakes score higher but offer higher performance levels. This makes the most preferred types of brakes. Today, there are even conversion kits for car owners who may want to change from drum to disc brakes. Despite their high cost, these disc brake types offer reliable braking for driving safety.

Disc brake systems come with specifications that are necessary to ensure optimal performance and guaranteed braking. Let us see about these specs in the next chapter.

Chapter 2

Disc Brake Specifications

Disc brakes are made to specific characteristics. This ensures they satisfy various requirements for performance, fit, lifespan, safety, and more. It is also what enables disc brakes to follow certain standards. Technicians use a brake specifications guide when servicing brakes to ensure the various parts are within the requirements. The disc brake specifications range from dimensions, torque levels to materials and design.

Disc Brake Specifications Chart

Different parts of the disc brake system have specific values for dimensions and torque. Here is a specifications chart for the various components that make a disc brake system.

Disc Brake Component (all models)Standard specsService Limit Specs
Master Cylinder Bore Inside Diameter0.5512-0.5529in.0.5543in
Master Cylinder Piston Outside Diameter 130.5495-0.5506in.0.5472in
Master Cylinder Cups Outside Diameter0.5768-0.5965in.0.5709in.
Master Cylinder Spring Free Length2.169in.1.89in.
Caliper Bore Inside Diameter1.5031-1.5039in.1.5045in.
Caliper Piston Outside Diameter1.5006-1.5019in.1.5002in.
Disc Thickness0.276in.0.217in.
Disc Runout00.012in.
 Disc Brake Torque Specifications
Brake Lever Pivot Bolt3.5 ft-lbs.
Brake Lever Adjuster6.0 ft-lbs.
Master Cylinder Clamp Bolt4.5 ft-lbs.
All Banjo Bolts
All Brake Pipe Fittings12.0 ft-lbs.
Three-Way Fitting Mounting Bolts13.0 ft-lbs.
Hydraulic Brake Light Switch13.0 ft-lbs.
Caliper Shaft22.0 ft-lbs.
Bleeder Valve6.0 ft-lbs.
Disc Mounting Bolts12.0 ft-lbs.
Disk Brake Materials
Source : http://www.classicindustries.com

Disc Brake Materials Requirements

Disc brake materials determine the strength and performance, and durability of the particular component. This, in turn, influences the amount of braking power achieved and safety when driving. If the parts are not manufactured to the required specifications, they break easily and cannot cope with the braking conditions such as friction, load, heat, and the elements. The disc brake specs for material requirements include:

High Strength In Excessive Temperatures

Brake rotor and pads are usually subjected to very high levels of heat. During extreme braking conditions, the heat can reach high levels as to cause thermal distortion or even melting. These parts must, therefore be made from materials that can withstand high temperatures without damage.

High Stiffness

The brake disc, brake rotors, and the calipers need to withstand the braking force, vibrations during driving, and physical impact. They should be stiff enough to resist breakage by maintaining structural integrity in the harshest of conditions.

Low Density

The braking components of a disc brake system are many at the wheel, which means extra weight.  If made from heavy materials, the parts can weigh down the vehicle and affect the free movement of the suspension. That is why the disc brake materials used need to be lightweight, especially the calipers.

High Thermal Conductivity

As we have seen, brakes generate a lot of heat. This can cause damage or even start a fire. Because of this, the rotor is made from a material that possesses good thermal conductivity. Such rotors dissipate heat rapidly to avoid damage and other problems.

High Abrasion/Corrosion Resistance

This prevents wear of the materials that are exposed to corrosion and wear. Components that are prone to wear include the brake lines and hoses, calipers, the rotor, and the brake parts. The rotor and the pads are especially prone to abrasion and the reason they are made from advanced materials.

Excellent Creep Resistance

The metal parts of the disc brake system can creep and cause the brakes to malfunction. This necessitates proper caliper, brake line, brake pad, and brake disc material selection during manufacture.

Low Noise

In addition to using several components and technologies to reduce noise, the parts of the disc brake system are themselves made from low noise materials. This helps to reduce the sound produced by braking which, if not checked, can be abnormally high. The only noise then becomes that of a faulty braking system.

Shows sample images of brake disk design
Source : http://www.cquence.net

Disc Brake Design

This involves the dimensions and shaping of the various disc brake components. The vehicle application usually influences the design of disc brakes. Heavy-duty braking requires different brakes from those used for light braking.

That is why the disc brakes of heavy trucks feature a design that is different from that of normal passenger cars. The calipers may be larger, with a higher number of pistons, and made from stronger materials.

The brake rotors of heavy vehicles are designed differently from those of light cars. They may be vented to dissipate heat better, or have holes drilled on them to prevent gas and heat buildup.

Race cars will have uniquely designed brakes to suit the heavy braking situations. On the other hand, the regular passenger vehicle will do with the standard designs for the disc brake components. The rotor may be the flat type and the caliper single piston.

Chapter 3

Parts Of A Disc Brake System

Disc brakes are complex systems that consist of different components. These are mostly pistons, push rods, tubes, levers, and other parts in the length between the brake pedal and the brake rotor. Every part of the disc brake system performs a useful function. If any the components break down, the results can be reduced braking power or brakes that fail completely. In this part of the disc brake guide, we look at the main components of disc brakes.

Major Disc Brake Parts

Tracing them from the pedal to the rotor, they include the master cylinder, the brake lines, the brake caliper, brake discs, and the brake pads. Let us look at each one of them.

The Master Cylinder
Source : http://www.quadratec.com

The Master Cylinder

In a disc brake system, the master cylinder can be said to be the hydraulic pump. It helps to push brake fluid into the brake lines towards the calipers for braking to occur. When you depress the brake pedal to stop a vehicle, you are essentially moving a piston in the bore of the master cylinder to compress the hydraulic fluid.

The disc brake master cylinder, together with the brake booster unit, is designed to amplify the force of the pedal many times and send that pressure to the calipers. A reservoir continually fills the master cylinder with braking fluid to keep it air-free. That’s because air can affect the performance of the hydraulic fluid and result in reduced power to stop a vehicle.

To ensure the master cylinder can serve its function effectively, it needs to be maintained. This usually involves checking it for wear and leaks and ensuring adequate brake fluid in the reservoir. If air happens to enter the master cylinder, it is necessary that you bleed it to restore fluid pressure.

The brake line and horses
Source : http://www.summitracing.com

The Brake Lines And Hoses

These are the tubes that carry hydraulic fluid from the master cylinder to the brake calipers. They are the passageways that allow the force of the brake pedal to the brake pads and therefore, the rotor. Brake lines are made of steel, while brake hoses are rubber tubes and can flex to allow the up and down movement of the brake calipers.

When you press the brake pedal, brake fluid moves from the master cylinder into the brake lines and hoses. These then take the fluid to each wheel, allowing the pressure from the master cylinder to be transmitted to every caliper with equal force.

Brake lines and hoses, simple as they may appear, are essential parts of the disc brake system. If they happen to break or develop a leak, the hydraulic fluid pressure drops considerably and braking power is affected. These should, therefore, be inspected regularly to ensure they are in good condition at all times.

Brake Caliper Image
Source : http://www.applehydraulicsonline.com

The Brake Calipers

Calipers are the vices that clamp the brake disc to enable the pads and the disc to make contact. These components consist of pistons, which can be one or several. Caliper pistons are connected to the hoses that carry the hydraulic fluid and sit in their bores when you have not stepped on the brake pedal.

When you apply the brakes, the resulting pressure on the brake fluid causes the caliper pistons to move. It is this movement that squeezes the pads to the rotor and causes the vehicle to stop. When the brake pedal is released, the pistons are pulled by the return springs back into their bores.

Brake calipers serve one of the most important functions in a disc brake system. Without them working correctly, the pads may not make proper contact with the rotor. This can cause dangerous situations, especially when driving at high speeds. Regular inspections of the disc brake caliper assembly help to prevent that from happening.

Brake Disk
Source : http://www.tomson.com.pl

The Brake Discs Or Brake Rotors

These are the round discs that spin together with the wheels and which, when pressed by the brake pads, stop spinning and cause the wheels also to stop. Brake discs can be made from different material with ceramic rotors being the best. Rotors made from this material are durable, handle heat better, and are highly resistant to damage among other attributes. Other brake disc materials include steel, cast iron, carbon, and aluminum.

Disc brake rotors can also be of different designs. They can be vented, slotted drilled, or a combination of two different designs. Modern rotors also feature designs not seen before such as dimpled surfaces and scalloped edges.

To perform as expected and stop a vehicle when needed, a brake disc has to be damage and wear-free. It also has to be within certain specifications. The rotor specs are usually written on its body and vary across different models and designs. Inspecting the disc from time to time helps to spot problems early and avoid cases of failed brakes.

Brake pads Sample Image
Source : http://drivinglife.net

The Brake Pads

These are the pieces that press against the brake disc to cause the friction that stops a vehicle. Disc brake pads consist of a metal backing and frictional material on the surface that squeezes the brake rotor. These components are one of the most replaced in a disc brake system, and for a reason.

During braking, the pads wear out a frictional material that gets deposited on the rotor surface. This material causes the two surfaces to stick together, enhancing the braking force. But that also causes the brake pads to wear out more quickly.

To ensure efficient braking and protect the rotor against grooving, disc brake pads should be replaced in time. Worn pads will have reduced performance. If the metal backing is exposed, there is the risk of damage to the rotor surface due to the scoring action of the metal studs or steel backing.

This disc brake parts diagrams show the components we have discussed above.

Over time and for one reason or another, a disc brake system develops problems. These can affect one or several of the components. What are some of these problems? Find out in the next chapter.

Chapter 4

Disc Brake Problems

Brake discs consist of different parts. That increases the likelihood of faults in the brakes as one bad part affects the whole system. However, spotting problems early usually helps avert serious issues. It allows you to fix brake systems failures before they worsen to cost you new parts. But that requires you to know what problems can affect the disc brake systems.

Let us have a look at the common problems of the brake disc system.

Clear and contaminated brake fluid
Source : http://elitemotorsoc.com

Contaminated Brake Fluid

A vehicle’s brake fluid is supposed to operate under ideal conditions where it doesn’t come into contact with dirt, grime, and moisture. But that does not usually happen. In one way or another, contaminants may get into the master cylinder or the brake lines and hoses.

When that happens, we say the brake fluid is contaminated. Its ability to produce braking pressures drops and the effect can be felt in many ways. Some of the problems caused by these contaminants include a chemical breakdown of the fluid and the rusting of the metal parts in the brake system.

The problem of bad brake fluid is usually solved by flushing it out and putting in new fluid. This removes the dirt particles, moisture or air to bring the performance if the brakes to normalcy. But how do you know that you have contaminated brake fluid?

If the ABS light comes on, it could mean a leaking brake fluid that has let in contaminants. A spongy pedal may also indicate brake issues, among them dirty brake fluid. If your car pulls to one side when you ally the brakes, that could mean leaks in the brake fluid systems among other causes.

It is often recommended to flush brake every 30, 000 miles. However, some conditions may cause you to carry out the maintenance earlier than that. If you drive in situations that require you to uses the brakes a lot, for example. The demand for braking can cause air to enter the fluid systems. Also, if you have been carrying out repairs on the brake system to expose the brake fluid to contamination.

A leaking master cylinder
Source : http://bbs.zuwharrie.com

Brake Lines And Master Cylinder Problems

One of the most common problems with these components of the brakes is leaking fluid. Leaks can develop from many causes but mostly as a result of wear that occurs over time. Worn rubber seals on the master cylinder can cause reduce the ability of the master cylinder to hold in fluid pressure. This often manifests as a soft brake pedal.

If the master cylinder and the brake lines are leaking hydraulic fluid, the results can be felt and seen. It could be visible leaks that show up the brake fluid. Another sign is brake fluid level in the master cylinder dropping significantly. Low fluid level can result from brake pad wear. However, the drop of fluid level caused by leaking is often drastic.

Low fluid levels can also cause the brake pedal to drop to the floor too easily. In the worst of cases, this can cause dangerous lack of brakes when you need to stop a vehicle. Regular inspection of the master cylinder for wear and leaks can help prevent these problems. The brake lines and hoses, too. And if there are signs that anything is not fine, prompt repair or replacement of the damaged part is recommended.

A damaged caliper piston
Source : http://www.toyota-4runner.org

Brake Caliper Failure

When operating normally, the calipers will push the brake pads towards the rotor when you apply the brakes. This decelerates or stops the vehicle as required and makes the disc brake system to operate efficiently. However, the brake caliper can fail in different ways, making braking less reliable or unavailable altogether.

Brake calipers may stick due to a number of reasons. Usually, caliper pistons are protected by a rubber seal. If this wears out or gets damaged during servicing activities, debris may find a way into the piston bore and cause the calipers to seize. Dirty caliper slides and bolts can also cause a similar problem. However, that can be corrected easily by cleaning out the debris.

Leaking brake fluid reduces the pressure to move the pistons. This results in weak braking overall. Apart from the reduced braking force, a leaking caliper can be confirmed if there is an oily patch on the ground just underneath the caliper position.

Age and the elements can also take a toll on the brake caliper. Several parts may be too worn to function correctly, especially the pistons. Depending on the driving conditions or vehicle storage, the caliper assembly can corrode over time and make the caliper to fail. Should that be the case, replacement is usually the best option. If there is not much damage, a rebuild of the caliper is usually enough to fix the problem.

Rotor or disc brake problem
Source : http://www.depaula.com

Brake Rotor Or Brake Disc Problems

A crucial component itself, a bad brake rotor can cause a disc brake system to fail. The brake disc provides the surface that causes friction to stop a vehicle. If this surface happens to be in bad condition, it can mean breaking that is significantly affected.

One of the most common problems with brake rotors is warping. This usually results from the constant heating and cooling that causes some parts of the surface to rise. The surface then becomes uneven. Besides causing reduced braking force, the warped rotor often makes the brake pedal, steering wheel, and chassis to vibrate. It can also cause annoying noise.

Brake rotors can also wear too much and become liable to cracking, warping, or breaking. Sometimes, the rotor becomes scored by worn brake pads metal studs or steel backing or corroded by rust. All these forms of damage affect the quality of the rotor’s frictional surface. The result is reduced braking force, especially if the vehicle application requires heavy duty braking.

Damaged or warped rotors can be resurfaced or replaced. The choice depends on several factors such as nature and extent of the damage. The budget, too, as some rotors can be quite expensive. Brake rotors are easy to access and can be checked frequently even without removing the wheel.

bad brake pads

Bad Brake Pads

These components are part and parcel of the disc brake system. If they are not working as expected, the other parts cannot be of any use when it comes to stopping a vehicle. Brake pads provide the frictional material that rubs against the rotor. For this reason, the water rapidly and needs to be changed more frequently.

Worn out brake pads can cause noisy braking. If the wear has eaten away at the lining, the metal backing of the pads will grind and damage the rotor surface. You may also feel the brake pedal pulsate which can affect driving comfort.

When the brake pads heat up too much, the braking response lowers. This can affect the overall performance of the brakes to cause safety concerns. The loss of braking power due to heating becomes more apparent when constant braking is necessary, such as when driving on hilly places.

Now that we have seen the major problems that affect disc brake systems, how can you tell when they do occur? The next chapter is all about that.

Chapter 5

Symptoms Of A Failing Disc Brake System

Disc brakes consist of various components. These can fail at any time, either from aging or as a result of damage. Luckily, faulty brakes often give clear signals before the problem worsens. These symptoms are either distinct to the malfunctioning component or the braking system in general.

Knowing what problem gives what sign is essential. It helps a vehicle owner to identify the components that have become faulty. One can then take the appropriate action and on the right part. At the earliest opportunity, too, which goes a long way towards ensuring driving safety.

Signs That A Brake Disc System Is Not Working Correctly

There are many signs of faulty brakes as we highlight here.

ABS dashboard brake light

Dashboard Brake Light

Your car’s brake system is served by two warning lights: the red handbrake light and the orange ABS light. That depends on the car make, though, and may not apply to all vehicles. If one or both lights come on, it can mean brakes that need to be checked.

A brake warning light is often a sign of low brake fluid levels- mostly due to leaks or worn pads. Since the light can be on when the parking brake is set, you need to rule out that first. Release the parking brake, and see if the light goes off. If it stays on, something the problem could be the brakes.

The max and min levels for the master cylinder brake fluid
Source: http://thehappycar.com

Low Brake Fluid

Low brake fluid can indicate worn brake pads or a leak in the fluid system. As the pads wear out, the level of brake fluid in the reservoir keeps dropping. This is normal and will normalize once you replace the pads.

If the fluid level is caused by a leaking brake line, hose, master cylinder, or leaking caliper, the problem needs immediate attention. It can lead to excessively low hydraulic pressures and cause the brakes to fail. If you notice low fluid levels, inspect the master cylinder, brake hoses, brake lines and the brake calipers for leaking brake fluid.

Grinding Noise

This noise indicates a metal to metal contact between two parts in the brake system. It could be worn brake pads, a seized caliper. The grinding sound is often caused by the metal backing of the brake pads coming into contact with the rotating rotor. If left to continue a little longer, this can cause irreparable damage to the rotor’s surface.

Grabby Brakes

Brake pads that have oil, grease or hydraulic fluid on them will slip and grab. This causes jerky braking. Rotors that are excessively scored can also cause grabby brakes. If brake system is providing too much pressure, or the pads an increased friction coefficient, the brakes will become grabby. The eliminate this problem, it is necessary to replace the contaminated brake pads. Find the source of the contamination, too, and fix it. For the groove rotor, you may have to machine it or install a new one.


Squeals can happen either during braking or when you have not pressed any brake pedal. In a disc brake system, a squeal when you apply the brakes could a sign of worn brake pads. Some types of pads utilize a metallic stud that, when exposed as a result of pad wear, contact the rotor to produce brake noise and alerts you of the wear. If that is the case, changing the pads solves the noise problem.

There are other possible reasons for this kind of noise. It could be a worn or warped rotor.

Brake Pedal Symptoms

The feel and behavior of the brake pedal can indicate brake problems in many ways. The signs to look out for include.

  • Pulsation

This is one of the worn brake disc symptoms. A faulty caliper can also cause the pedal to pulse. When the brake rotor warps, the uneven surface sends the brake pads in and out rapidly as it revolves. These vibrations get transmitted to the pedal, causing the pulsations. The steering wheel also wobbles. Resurfacing or replacing the affected brake rotor corrects the problem.

A seized caliper whose pistons cannot return into their bores could also cause a pedal to pulsate. The caliper remains clamped on the rotor and you feel that as vibrations and wobbliness at the foot and in the hands. Cleaning the caliper is one of the remedies to this problem. Or, in severe cases, replacing or rebuilding the affected caliper.

  • Spongy Or Soft Feel

Air in the brake fluid system can make a brake pedal soft.  Also, low levels of the hydraulic fluid. Air can gain entry into the hydraulic fluid as a result of either leaks, reduced fluid levels, or incorrect bleeding. A soft pedal can also result from a brake hose that bulges during braking to cause loss of hydraulic pressure.

Air in the brake fluid can be removed by bleeding the brake lines. But you would need to inspect the brake lines first to see if there are leaks. The caliper and master cylinder, too. If leaking fluid is observed, replacing the broken part of the brake fluid system is usually necessary.

To prevent this brake problem from occurring, ensure proper levels of the brake fluid in the master cylinder at all times. You may also have to bleed the brake lines using the correct procedure if you did it wrong and ended up introducing air in the system.

  • Excessive Travel

Excessive travel of the pedal can be caused by air in the brake fluid or worn brake pads. The danger in this is the reduced response of the brakes. In severe cases, the pedal may depress to the maximum before adequate braking is achieved.

Pumping at the pedal can help work around the problem. But that is only a temporary solution to a dangerous problem. It is advisable that you bleed the fluid system promptly. And if the problem is caused by worn brake pads, replace them without delay.

  • Sinking Pedal

This happens when you lightly place your foot on the pedal and it sinks slowly to the floor level. If a brake pedal goes to the floor, it indicates a master cylinder that cannot hold hydraulic pressure. This is often caused by leaks. Unless this problem is solved by checking the brakes system for leaking brake fluid, driving the car would be unsafe.

  • Hard Pedal

This is often caused by a faulty brake booster. The booster sits between the brake pedal and the master cylinder and amplifies the force produced by the brake pedal. That way, you do not use a lot of effort on the pedal during braking.

When the brake booster fails, braking assist is lost and the pedal feels hard to depress. The problem is often caused by a leaking vacuum hose or bad check valve. It can be corrected by shutting the engine and pumping the brake pedal to bleed out the remaining vacuum out of the booster. When the engine is started, the pedal should feel lighter. If not, the brake booster may need to be replaced.

Vehicle Pulling To The Side

This is usually a sign that one side of the brakes is not working properly. The vehicle swerves to the working side since the rotor there stops the wheel from spinning. Because brake failure can have many causes, you may need to check the failed side for several problems. These include warped rotors, worn pads, leaking or seizing calipers, leaking brake lines or master cylinder, and more.

Vehicle Travels Too Far Before Stopping

This can be caused by inadequate hydraulic pressure as a result of leaks in the hydraulic system. Brake fluid leaking from a caliper or brake line can be seen on the ground as an oily spot. Worn brake rotors and pads can also cause prolonged stopping distance. To remedy this problem, check and replace or repair the faulty parts.

Burning Smell

This is usually a sharp odor of something burning. In severe cases, you may notice smoke at the wheel. A burning smell is often a sign of sticking caliper that keeps the pads squeezed against the rotor to produce heat. Excessively hot brakes are not effective, and may not stop a vehicle when required. If you notice that, it is advisable to check the caliper for seizing and replace or rebuild it.

Leaking Brake Fluid

This is an obvious symptom of bad brakes that can be observed easily. A leaking brake caliper or brake lines will drip the fluid on the ground and create an oily patch. Leaking brake hoses can be seen to be covered with the hydraulic fluid. The same case with a leaking master cylinder.

Chapter 6

Brake Disc Troubleshooting And Diagnosis

The braking system of a vehicle needs to be in good condition at all times. That is because it determines driving safety and faults can be dangerous. To ensure the brakes are working correctly, it is essential to perform tests and inspections from time to time. These will help you catch malfunctioning components early on to avoid further damage. Here, we will show you how to carry out disc brake troubleshooting by testing and inspecting the various parts.

Brake Disc Part
Source: http://www.lesschwab.com

Brake Pedal Tests

The pedals can help indicate if there are problems in the braking system. To perform the pedal tests, find a quiet place with no traffic. It can be a parking lot or an empty street. Ensure the engine is on and the car in neutral or parking gear position.

  • Step on the pedal and see how much down it goes before it begins to offer resistance. The distance before resistance should not exceed a quarter of the total distance from the rest position of the pedal to the floor. If it depressed excessively to engage the brakes, there could be a leak in the fluid system, or the brake power booster could be faulty.
  • Depress the pedal a little harder and for some time to see if eventually starts to go down when you keep pressing. If it does, you might be having a leak in the fluid system.
  • Pump at the pedal a few times and in quick succession and note the position at which it stops. If it is higher than when you started, it could mean you have air in the fluid system.
  • If the pedal feels too hard, the problem could be a faulty brake booster or blocked brake line. This component requires the help of a professional to diagnose and you may have to take the car to a mechanic for that.

Performing Brake And Pedal Tests

Next, test the pedal and the brakes while the vehicle is in motion. Release the parking brake and engage the transmission. Put it in drive gear.

  • Step on the brake pedal and listen for any sounds that may come on when you apply the brakes and disappear when you release the pedal. The brakes will produce some noise, which is normal. But when the sounds are high and irregular, it could indicate a problem with the system- mostly at the rotor or pads.
  • Feel for any vibrations in the pedal which could be a signal that the rotor is warped. If the vibrations are intense, they could also be a sign that the rotor is badly damaged.
  • Accelerate slightly depending on the conditions of the place you are at then brake sharply. A faulty brake will cause the car swerve to one side. The problem could be a sticking caliper that is not releasing the rotor.
Inspecting the rotor and calipers
Source : http://thingsautos.com

Visual Inspections

Park on flat ground and away from both human and vehicle traffic. Jack up the car and place wheel stands.

  • Start by visually inspecting the rotor with the wheel on. If the rotor is in good condition, its surface should be smooth and uniformly colored (and shiny). If there are grooves, scrapes, or raised spots, there is damage already. If the rotor surface is purple or blue colored, too. A bluish appearance means the rotor has overheated and could be a sign of possible warping.
  • Spin the wheel and listen for any contact sounds. If you have someone with you, you may have them apply the brakes while you check to see if the wheels come to a stop.
  • Check the brakes on each wheel to ensure each is working properly.
  • Examine the brake lines and hoses for wear, corrosion, and leaks. If you observe any leaks, change the affected part promptly. Old brake lines may have corroded over time and may be openly damaged. These need replacing.
Low Fluid Levels
Source : ifixit.com

Checking The Brake Fluid Level And Pressure

Low fluid levels and pressure cause reduced braking power and the soft pedal symptom. Here is the process on how to check brake fluid amount and pressure levels.

  • Check the level of fluid in the master cylinder reservoir. It should not be below the minimum. Note that it is normal for the level to drop slightly with the wear of the brake pads as this creates space in the fluid system at the calipers. When you install new pads, the fluid level should adjust to normal.
  • If the brake fluid is below the minimum level, you may have to top it up. Low levels can lead to the entry of air into the system and cause braking problems.
  • If the pedal lacks braking pressure, you may be having a faulty master cylinder, which may need to be replaced.
  • If the pedal feels spongy, bleed the brake fluid system ( brake lines and master cylinder) remove the air that could be present in the braking fluid.

Inspecting The Brake Calipers, Brake Rotors, And Brake Pads

Let us now look at how to troubleshoot brake problems by checking parts that are located at the wheels: the caliper, brake disc, and the pads.

The Disc Brake System
Source : http://www.autorepairchanhassen.com

  • Inspecting The Brake Caliper

Locate the brake caliper which is the assembly that holds the brake pads and sits clamped on the rotor. Check it for corrosion, rusting, and wear. The piston should be in good condition with the seals intact and debris-free. Observe to see that there are no leaks. For the floating calipers, the slides should be clean and adequately lubricated. Ensure the caliper pistons are fully retracted. If you observe any damage, you may need to replace the whole assembly or fix the broken parts.

  • Inspecting The Rotor

Check to see that the rotor surface is shiny and evenly smooth. Bluish or purple color indicates overheating, which is not a good sign. With the rotor now accessible, you can check it for warping or ascertain thickness. Use a micrometer to measure thickness, and a dial indicator for lateral runout.

  • Inspecting The Pads

Worn brake pads can cause problems with the braking system. Here is how to check brake pads for wear: Without removing the caliper, locate the brake pads. Use a compass to measure the pad thickness. This will show you the amount of wear. Insert the points of the compass to touch either side of the pad. Then, place the compass points on a caliper or tape measure to get the width of the brake pad. If the pads are less than ⅛ of an inch, replace them promptly. If they are ¼ of an inch thick, you may have to change them soon.

Note that the method described here will not provide you with adequate information about the stated of the brake pad. For a thorough inspection, you may have to remove the caliper. Do this if you suspect the pads to be badly worn out.

Chapter 7

How To Maintain A Disc Brake System

Most of the time, the components in a disc brake system get damaged due to neglect. Not taking good care of the brake system causes problems to develop, existing faults to worsen, and brakes to fail. This leads to costly component repairs or replacements. Above all, it results in a vehicle that is unsafe to drive.  In this chapter of the disc brake guide, we will look at the way to keep your car’s braking system in perfect condition at all times.

The brake fluid image
Source :http://www.carztune.com

Brake Fluid

Braking systems that use hydraulic fluid often experience fluid contamination. Hydraulic fluid is hygroscopic, which means it will easily attract moisture. Moisture in the braking fluid can cause several problems. It corrodes the metal components of the brakes which reduces their lifespan.

Moisture also lowers the boiling point of brake fluid, causing it to boil in intense braking conditions. This results in vapor, which compresses easily and causes braking power to reduce. To avoid the moisture problems, it is essential to flush the brake fluid from time to time. It is recommended that you do a brake fluid change after every 2 years. That is about 30 thousand miles.

The brake fluid level should also be kept at the right level. Ensure it is between the “max” and “min.” If the brake fluid level is low, it can mean a master cylinder that strains. This causes various braking problems.

Cleaning the master cylinder
Source : http://www.evolutionm.net

Brake Lines And Master Cylinder

The master cylinder provides the hydraulic pressure to work the brakes. If it fails, it can mean low fluid pressure and reduced braking power. There are a few maintenance practices you can observe to keep the master cylinder in good working condition. They are:

  • Ensuring no physical damage cracks, grooves, and corrosion on the master cylinder and brake lines are dangerous. They can lead to leaks.
  • Ensuring there are no leaks- inspect the brake lines and the master cylinder frequently for leaking fluid. Sometimes, it is a case of overfilling the master cylinder and which may require draining. But then, you need to know how to drain brake fluid from the reservoir correctly. You also need to know how much brake fluid should be in the reservoir as too much or too little of it can cause problems.
  • Keeping the parts clean- ensure there are no corrosive materials on the brake lines and hoses. Dirt could cause the O-ring to get damaged, so keep the master cylinder itself and the area around it clean. When the master cylinder and brake lines are clean, you will spot leaks easily and take action early enough.
  • Bleeding- this helps to remove trapped air to restore braking force. It should be a regular maintenance practice. Air in brake lines is what causes a spongy feel of the pedal, one of the symptoms of faulty brakes. If the master cylinder cannot hold pressure during braking, it means there is air inside. Bleed it using the right procedure. Do the same to the brake lines if braking power is lost and air in the brake lines a possible cause.
Rebuilding a brake caliper can solve damage problems
Source : http://www.youtube.com

The Brake Calipers

Brake calipers contain moving parts and components that are prone to corrosion and dirt build up. If these are not taken care of, they may wear out or corrode to an irreparable state. The moving brake caliper parts may seize and cause braking issues.

To avoid all those problems, it is necessary to clean and lubricate the calipers regularly. Cleaning removes rust, dust, and debris which can accumulate and cause corrosion or hinder the free movement of the caliper’s parts. It is a simple process that takes an hour at the most.

After cleaning the caliper, apply brake caliper grease to the slide pins if your car uses the floating type. Ensure, too, that you tighten the loose bolts. Badly damaged calipers need to be replaced as driving with such can be risky. For slight damages, you may consider replacing the faulty part or parts. There are repair kits you that you can purchase for to rebuild a malfunctioning caliper.

The Brake Caliper before and after
Source : http://empoweredautopremium.com

Brake Rotors And Brake Pads

These are the frictional parts of the disc brakes that contact to stop a vehicle. The friction makes them wear out fast, so you need to keep checking them regularly. If you notice any sign of damage or wear, it is advisable to do repairs or, if necessary, replacement.

One of the mistakes vehicle owners make is letting the brake pads wear out completely. This causes damage that may lead to early brake rotor resurfacing or even replacement. The rotor is mostly visible through the wheels. Frequent observations help you to notice worrying colors, spots and scoring early enough.

Driving Advice To Help Protect The Brake Rotor And Pads

To prolong the life of the brake rotor and the pads, you need to observe a few driving tips.

The stop and go driving strains your braking system and causes the various parts to wear quickly. Avoid that if possible. Also, keeping your foot on the brake pedal even when you are not stopping the vehicle is not advisable. The habit reduces the lifespan of the brake rotors and pads significantly.

When driving in high traffic areas, it is advisable to leave space between your car and the one in front. It allows you to decelerate without having to apply the brakes sharply. Aggressive driving can also take a toll on your brakes. It causes you to pump on the pedal constantly causing them to wear out or the rotor to warp.

Keeping your disc brakes working correctly involves taking care of the different parts. That is because every component plays an important role. While some maintenance practices can be DIY, there are those that require a professional. However, most are simple and you can do them yourself.


Disc brakes are the most common braking systems today. Unless your car is an older make, you will have them either on the front or all the four wheels. A disc brake system offers reliability even in harsh conditions. They are also durable and will serve you for years. But that is only possible if the brakes are well-maintained as faults can cause the brakes to fail and the lifespan to reduce considerably.

After reading through this disc brake guide, you now know what the different parts of the disc brake do and what can damage them. Understanding the brakes in your car is the first step towards taking care of them. Disc brakes have the advantage of accessibility which makes inspecting and fixing faults easy. When you know the signs to look out for, you can troubleshoot the brake system easily.

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