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How Does it Work /
Disc Brake
How a Disc Brake System Works
Brake systems are designed to slow the vehicles wheel movement through friction.
There are primarily two brake systems, ABS and non ABS (anti brake skid). Both systems
work on basic hydraulics and utilize a
brake master
cylinder (connected to the brake peddle in the car) that supplies brake fluid
pressure to the
front brake calipers
and rear wheel cylinder
or brake calipers
if so equipped.
Typical Non ABS Brake System
The brake system requires hydraulic force which is many times greater than the
force applied by the foot. This added hydraulic force is achieved by leverage multiplication.
The multiplying force can be changed by varying the relative location of the brake
master cylinder rod pivot as it relates to the lever.
In the hydraulic force multiplication method, the force which is applied at one
point is transmitted by incompressible brake fluid to another point. This basic
system consists of two pistons (master cylinder and wheel caliper or cylinder),
which are filled with brake fluid and are connected by a brake line of any length
or shape. When the brake peddle is forced down brake fluid from the master cylinder
is transferred to the brake caliper piston, pressurized fluid is transmitted through
the brake caliper to the brake pads or shoes, which are mounted to the brake caliper
or wheel cylinder.
A major problem to the brake system is a brake fluid leak, if there is a slow
leak in the system it will effect the brake master cylinder by allowing air into
the system creating a low peddle and eventual brake operation failure. If a large
brake fluid leak is present, fluid escapes, leading to a major brake failure on
one half of the system (front or rear). A master cylinder has a built in safety
device, two separate hydraulic systems a primary and secondary, separating front
and rear brake operation incase of front or rear brake operation failure, one system
will still be present.
Common Problems and Fixes
Today's brake systems are reliable and easy to maintain, most systems are designed
for easy service and
brake pad replacement.
If the brake pedal becomes hard to push, there can be a possibility of a broken
vacuum supply line or a failed power brake booster. It is also very important to
use the correct type of brake fluid, otherwise the brake system can malfunction.
This can lead to problems such as spongy feeling pedal and the brake pedal travel
becoming excessive. Only the highest quality brake fluid must be used in a brake
system and must never be reused and must always be discarded immediately after the
fluid storage container is opened to avoid moisture contamination. When adding brake
fluid to the master cylinder care must be taken make sure brake fluid is not spilled
on the paint of the car, brake fluid is very corrosive and will destroy the paint.
Squealing brakes is an indication of a problem with the brake system. Most of
the time a squealing noise can be a warning to you that your
brake pads are worn down and need to be replaced. Other causes can be overheated
brake pads or rotors and sometimes rust can get impregnated on the brake lining
material and cause grumbling or squeaking noises.
When cleaning brake components prior to service precaution must be taken. Most
brake systems contain asbestos fibers that are extremely hazardous to your health.
While cleaning with brake system cleaner there is an increased chance of inhaling
these fibers which accumulates on the brake components. Cleaning should be done
in a well ventilated area, use an air filter respirator if possible for best results.
Basic Maintenance
It is important to inspect your brake system periodically. Check the level of
brake fluid and the thickness of the brake pads or shoes. Before checking the brake
fluid level, the cover of the master cylinder must be wiped off so no foreign material
can fall inside the reservoir. The
brake pads and
brake
shoes should be periodically inspected from the amount of wear the brake pad
has endured and replace as needed.
ABS Anti Brake Skid
The
ABS brake system is a computerized wheel speed system that can detect when one
or more wheel is not rotating as fast as the other wheels and will dump brake pressure
to those wheels until the wheel (or wheels) can maintain equal rotation. ABS brake
systems utilize a series of wheel speed sensors, a brake control module and a main
ABS control unit. The ABS control unit controls and monitors the ABS brake system.
These brake components transfer evenly dispersed brake fluid pressure to the brake
pads and shoes and keep the vehicle under control. (for more info
ABS brakes)
Brake Fade
Brake fade is a condition that occurs when the brakes on the vehicle stop working
even though there is good peddle and no obvious problem with the brake system. This
condition can present itself when the brake system is overheated. When friction
is applied to a rotating mass (brake rotor or drum) the energy is transferred into
heat, when the brake rotor is over heated it cannot absorb any additional heat.
This will cause the brakes to fail no matter how hard the brake peddle is applied.
This condition can occur when braking down long grades and in high performance driving
applications where repeated acceleration and braking occurs over a short period
of time.
Brake System Maintenance and Inspection
Brake system maintenance is crucial. To keep your vehicles brake system serviced
correctly flush your brake fluid every 25,000 to 35,000 miles. Inspect brake fluid,
master cylinder, pads, flex hoses and shoes for fluid leaks regularly. When replacing
brake system components always use top quality OEM (original equipment manufacturer)
brake parts. Many inexpensive brake parts will, squeak, grumble and need replacement
sooner.
Brake Proportioning or Combination Valve
The proportioning or combination valve is located inline with the front and rear
brakes. This valve is used to monitor the brake system pressure from front to rear
and warn you of a fluid pressure drop is detected. When a system failure is detected
a brake warning light is illuminated on the instrument cluster.
Emergency Brake
A car emergency brake performs two operations, it helps hold the car when parked
on a hill, plus it can help stop the vehicle if the conventional brake system has
failed. Inspect your emergency brake operation periodically to ensure proper operation
as part of a normal brake replacement and have the service technician inspect the
emergency brake system for wear and replace worn components as needed.
Brake Components
Power Brake Booster
A power brake booster utilizes engine vacuum to help pressurize the hydraulic system
in the car when the brake peddle is depressed.
Brake Pad Set
Semi metallic brake pads are generally made with copper, brass, and steel wool shavings
held together in a resin. Ceramic based pads are also available for high performance
applications.
Brake Disc
A brake disc is the rotating part of the braking system that contacts the brake
pads. Heat and energy are transferred from the brake disc to the pads while providing
friction to stop the car. Cross drill brake disc's help dissipate heat more efficiently
under extreme driving conditions.
Rear Brake Caliper
Brake calipers provide hydraulic pressure to the brake pads and apply friction to
the brake rotor to slow the vehicle.
Brake Master Cylinder
A brake master cylinder provides hydraulic pressure to the wheel cylinders and calipers.
Brake Shoe Set
The rear brake shoes are actuated by wheel cylinders that force the brake shoes
against the brake drum with hydraulic pressure from the master cylinder.
Brake Cylinder
Pressure from the brake system is applied to the brake cylinders forcing the brake
shoes against the brake drum.
How Does it Work
/ Disc Brake
Check Manufacturer Specific Brake
Pads Questions and Answers
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