Brake System Function
The brake system is probably the most important system in your vehicle. There’s no sense in making the car go if you can’t make the car stop. Over the years the brake system has evolved to be almost fool proof and with the introduction of the dual master cylinder, the possibility of total brake failure has virtually been eliminated.
When you depress your brake pedal, your car transmits the force from your foot to its brakes through a fluid. Since the actual brakes require a much greater force than you could apply with your leg, your car must also multiply the force of your foot. It does this in two ways:
- Mechanical advantage (leverage)
- Hydraulic force multiplication
The brakes transmit the force to the tires using friction, and the tires transmit that force to the road. This allows the car to stop.
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Brake System Components
There are a couple of problems with this simple system. What if we have a leak? If it is a slow leak, eventually there will not be enough fluid left to fill the brake cylinder, and the brakes will not function. If it is a major leak, then the first time you apply the brakes all of the fluid will squirt out the leak and you will have complete brake failure. The master cylinder on modern cars is designed to deal with these potential failures.
Most modern cars have disc brakes on the front wheels, and some have disc brakes on all four wheels. This is the part of the brake system that does the actual work of stopping the car. The most common type of disc brake on modern cars is the single-piston floating caliper.
The main components of a disc brake are:
- Brake pads
- Caliper, which contains a piston
- Rotor, which is mounted to the hub
The disc brake is a lot like the brakes on a bicycle. Bicycle brakes have a caliper, which squeezes the brake pads against the wheel. In a disc brake, the brake pads squeeze the rotor instead of the wheel, and the force is transmitted hydraulically instead of through a cable. Friction between the pads and the disc slows the disc down.
Drum brakes work on the same principle as disc brakes: Shoes press against a spinning surface. In this system, that surface is called a drum.
Many cars have drum brakes on the rear wheels and disc brakes on the front. Drum brakes have more parts than disc brakes and are harder to service, but they are less expensive to manufacture, and they easily incorporate an emergency brake mechanism.
The main components of a drum brake are:
- Brake shoes
- Brake drum
- Wheel cylinder or Brake cylinder
- Adjuster mechanism
- Emergency brake mechanism
Like the disc brake, the drum brake has two brake friction material sources (shoes for drum / pads for disc) and a piston. The drum brake system also has an adjuster mechanism, an emergency brake mechanism and lots of springs.
Many drum brakes are self-actuating which applies additional force to the drum. The extra braking force allows drum brakes to use a smaller piston than disc brakes. It also requires that the shoes must be pulled away from the drum when the brakes are released. This is the reason for some of the springs. Additional springs are needed to help hold the brake shoes in place and return the adjuster arm after it actuates.
To increase safety, late model car brake systems are broken into two circuits, with two wheels on each circuit. If a fluid leak occurs in one circuit, only two of the wheels will lose their brakes and your car will still be able to stop when you press the brake pedal.
The master cylinder supplies pressure to both circuits of the car. It is an amazing device that uses two pistons in the same cylinder in a way that makes the cylinder relatively failsafe.
The plastic tank you see is the brake-fluid reservoir, the master cylinder’s brake-fluid source. The electrical connection is a sensor that triggers a warning light when the brake fluid gets low.
When you press the brake pedal, it pushes on the primary piston through a linkage. Pressure builds in the cylinder and lines as the brake pedal is depressed further. The pressure between the primary and secondary piston forces the secondary piston to compress the fluid in its circuit. If the brakes are operating properly, the pressure will be the same in both circuits.
When the first circuit leaks, the pressure between the primary and secondary cylinders is lost. This causes the primary cylinder to contact the secondary cylinder. Now the master cylinder behaves as if it has only one piston. The second circuit will function normally, but you can see from the animation that the driver will have to press the pedal further to activate it. Since only two wheels have pressure, the braking power will be severely reduced.
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Brake – Trouble Symptoms
Squealing brakes can come from any vehicle that has drum or disc brakes or a combination of the two (disc brakes in the front and drum brakes in the rear).
Condition – Squealing brakes are the result of brake pads rubbing against the brake rotor, or perhaps, the brake pads in need of re-fitting to the brake caliper.
Solution – Serious problem that is more serious is the squeal that comes while driving but stops when you press your brake pedal. This is a symptom you absolutely must not ignore. Have your brakes checked by a mechanic right away.
Low Brake Pedal
Certainly brake pedals have various heights in different makes and models of vehicles and even in similar vehicles.
Condition 1- Adjust brake pedal – If your brake pedal becomes lower than it used to be, you’ll need to have your brakes adjusted or your brakes have become worn.
Condition 2- Self Adjusting Brakes – With self-adjusting brakes, choose a safe place and try backing up your vehicle and then suddenly braking. Do this three or four times, where you will not endanger pedestrians or hit another vehicle.
Solution – If this process doesn’t bring your brake pedal back to its normal height, you’ll need your brakes thoroughly checked.
Soft or Weak Brake Pedal
If you lose the firmness of your brake pedal or have to pump your pedal to stop your vehicle you may have trapped air somewhere in your brake hydraulic system.
Bleed the hydraulic system
This will require that you have the hydraulic system bled.
Replace your brake fluid
At this time, replace your brake fluid.
Always check your brake fluid levels before any long trip or extended high speeds, such as highway driving.
If you hear a grinding sound when you press your brake pedal, please take serious notice.
Do not put off this problem!
This is NOT a problem you can put off until tomorrow.
The grinding sound you hear is your brake pads or shoes which have worn down to the medal and there is no friction.
No Stopping Capacity
More directly stated there is NO stopping capacity.
In such a condition your vehicle may swerve or skid due to your brakes locking up.
Rather than merely relining your old brakes with new friction material consider making the investment in new brake shoes and lining that carry a life-time warranty.
The grinding sound, metal to metal, is a noise which indicates a serious brake problem
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Brake – Warranty
Clutch Mart offers the best Brake warranty in the industry. Under normal, non-commercial use, Clutch Mart installed parts are warranted for as long as you own your car.
Yes, a lifetime Brake parts warranty!
Replacement brake parts cost you nothing.
Our normal use (non-commercial) warranty is simple:
Parts – Lifetime warranty
Labor – Two years or twenty thousand miles (whichever comes first)
All warranty work becomes the top shop’s top priority – fix the problem fast.
Simple, fast, expert technicians, and low prices – your Clutch Mart advantage
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