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Brake System Basics 101

sperry

Silent Avalanche RIP
SM 2007
SM 2006
SM 2005
Full Member
Joined
Oct 22, 2003
Messages
13,160
Location
Seligman, AZ
This is not intended as service info. It's just for the curious!

Hydraulic Brake System Description and Operation

System Component Description

The hydraulic brake system consists of the following:

Hydraulic Brake Master Cylinder Fluid Reservoir

    Contains supply of brake fluid for the hydraulic brake system.
Hydraulic Brake Master Cylinder

    Converts mechanical input force into hydraulic output pressure.

    Hydraulic output pressure is distributed from the master cylinder through two hydraulic circuits, supplying front-rear opposed wheel apply circuits.
Hydraulic Brake Pressure Balance Control System

    Regulates brake fluid pressure delivered to hydraulic brake wheel circuits, in order to control the distribution of braking force.

    Pressure balance control is achieved through dynamic rear proportioning (DRP), which is a function of the ABS modulator. Refer to ABS Description and Operation in Antilock Brake System for specific information on the operation of DRP.
Hydraulic Brake Pipes and Flexible Brake Hoses

    Carries brake fluid to and from hydraulic brake system components.
Hydraulic Brake Wheel Apply Components

    Converts hydraulic input pressure into mechanical output force.

System Operation

Mechanical force is converted into hydraulic pressure by the master cylinder, regulated to meet braking system demands by the pressure balance control system, and delivered to the hydraulic brake wheel circuits by the pipes and flexible hoses. The wheel apply components then convert the hydraulic pressure back into mechanical force which presses linings against rotating brake system components.

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Brake Warning System Description and Operation

Brake Warning Indicator

The instrument panel cluster (IPC) illuminates the brake warning indicator when one or more of the following occurs:

    * The body control module (BCM) detects that the park brake is engaged. The IPC receives a class 2 message from the BCM requesting illumination.
    * The electronic brake control module (EBCM) detects a low brake fluid condition. The IPC receives a class 2 message from the EBCM requesting illumination.
    * The EBCM detects an ABS malfunction which disables dynamic rear proportioning (DRP). The IPC receives a class 2 message from the EBCM requesting illumination.
    * The IPC performs the bulb check at the start of each ignition cycle. The brake warning indicator illuminates for approximately 3 seconds before turning OFF.
    * The IPC detects a loss of class 2 communications with the BCM or with the EBCM.

Service Brake System Message

The service brake system message is displayed whenever the red brake warning indicator is illuminated.

Supplemental Brake Assist

The Supplemental Brake Assist (SBA) displays two messages through the Driver Information Center (DIC).

REDUCED BRAKE POWER

The REDUCED BRAKE POWER message is displayed when the supplemental brake assist signal circuit is held low. This happens when the SBA is active and maintaining reduced brake power levels.

SERVICE BRAKE BOOSTER

The SERVICE BRAKE BOOSTER message will be displayed when the supplemental brake assist signal circuit is toggled at 1.0 Hz with a 50 percent duty cycle. This message is also displayed if the instrument panel cluster (IPC) does not see an alive and well signal at key on. When this message is displayed it indicates a problem with the SBA and should be serviced or replaced.

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Brake Assist System Description and Operation (Hydraulic Assist)

System Component Description

The brake assist system consists of the following:
Brake Pedal: Receives, multiplies and transfers brake system input force from driver.

Brake Pedal Pushrod: Transfers multiplied input force received from brake pedal to brake booster.

Hydraulic Brake Booster: Uses power steering fluid pressure to decrease effort required by driver when applying brake system input force.
When brake system input force is applied, pressurized power steering fluid is admitted to the rear of an apply piston, providing a decrease in brake pedal effort required. When input force is removed, pressurized power steering fluid is blocked off from the piston.

Power Steering System: Supplies pressurized power steering fluid used by hydraulic brake booster to decrease brake pedal effort.

System Operation

Brake system input force is multiplied by the brake pedal and transferred by the pedal pushrod to the hydraulic brake master cylinder. Effort required to apply the brake system is reduced by the hydraulic brake booster.

Refer to ABS Systems 101 for further brake and stabilization system information.
 
Disc Brake System Description and Operation

System Component Description

The disc brake system consists of the following components:

Disc Brake Pads

    Applies mechanical output force from the hydraulic brake calipers to friction surfaces of brake rotors.

Disc Brake Rotors

    Uses mechanical output force applied to friction surfaces from the disc brake pads to slow speed of tire and wheel assembly rotation.

Disc Brake Pad Hardware

    Secures disc brake pads firmly in proper relationship to the hydraulic brake calipers. Enables a sliding motion of brake pads when mechanical output force is applied.

Disc Brake Caliper Hardware

    Provides mounting for hydraulic brake caliper and secures the caliper firmly in proper relationship to caliper bracket. Enables a sliding motion of the brake caliper to the brake pads when mechanical output force is applied.

System Operation

Mechanical output force is applied from the hydraulic brake caliper pistons to the inner brake pads. As the pistons press the inner brake pads outward, the caliper housings draw the outer brake pads inward. This allows the output force to be equally distributed. The brake pads apply the output force to the friction surfaces on both sides of the brake rotors, which slows the rotation of the tire and wheel assemblies. The correct function of both the brake pad and brake caliper hardware is essential for even distribution of braking force.

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Park Brake System Description and Operation

System Component Description

The park brake system consists of the following:

Park Brake Pedal Assembly

    Receives and transfers park brake system apply input force from driver to park brake cable system.

Park Brake Release Handle Assembly

    Releases applied park brake system when pulled.

Park Brake Cables

    Transfers input force received from park brake pedal, through park brake cable equalizer, to park brake apply lever.

Park Brake Cable Equalizer

    Evenly distributes input force to both the left and right park brake units.

    Threaded park brake cable equalizers are also used to remove slack in park brake cables.

Park Brake Apply Lever

    Multiplies and transfers input force to park brake actuator.

Park Brake Actuator/Adjuster

    Uses multiplied input force from apply lever to expand park brake shoe toward the friction surface of the drum-in-hat portion of the rear brake rotor.

    Threaded park brake actuators are also used to control clearance between the park brake shoe and the friction surface of the drum-in-hat portion of the rear brake rotor.

Park Brake Shoe

    Applies mechanical output force from park brake actuator to friction surface of the drum-in-hat portion of the rear brake rotor.

System Operation

Park brake apply input force is received by the park brake pedal assembly being depressed, transferred and evenly distributed, through the park brake cables and the park brake cable equalizer, to the left and right park brake apply levers. The park brake apply levers multiply and transfer the apply input force to the park brake actuators which expand the park brake shoe toward the friction surface of the drum-in-hat portion of the rear brake rotor in order to prevent the rotation of the rear tire and wheel assemblies. The park brake release handle assembly releases an applied park brake system when it is pulled rearward.
 
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