BRAKE SYSTEMS

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BRAKE SYSTEMS
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PURPOSE

• TO STOP THE VEHICLE IN THE SHORTEST DISTANCE
  POSSIBLE WHILE MAINTAINING CONTROL.

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How do Brakes Work

• Drivers need to be able to activate brakes as
  required
• This is accomplished by foot pedals or hand
  levers.

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How do Brakes Work?
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4 TYPES OF BRAKING SYSTEMS

• 1. HYDRAULIC
• 2. COMPRESSED AIR
• 3. MECHANICAL
• 4. ELECTRICAL

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HYDRAULIC BRAKING SYSTEMS

• PASCALS LAW
• WHEN A FORCE IS APPLIED TO A LIQUID IN A CLOSED
  CONTAINER IT IS TRANSFERRED EQUALLY AND
  UNDIMINISHED IN ALL DIRECTIONS.
• A FLUID TRANSMITS
• 1. MOTION
• 2. PRESSURE
• 3. FORCE

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Force Increase

• Brake force is increased by 2 methods
• 1) Hydraulic Advantage
• 2) Mechanical Advantage

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Hydraulic Advantage

• Fluids cannot be compressed
• A fluid pressurized by a small piston will move a
  larger piston with greater force, but less
  distance

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Levers
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Levers

• The brake pedal gives a mechanical advantage
  because it acts as a lever
• The input into the braking system is increased
  due to this advantage

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Hydraulic Circuits
Brake Caliper
Brake Warning Light
Wheel Cylinder
Rear Brake Lights
Master Cylinder
BRAKE PEDAL
Steel Brake Lines
Brake Caliper
Wheel Cylinder
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COMPONENTS

• MASTER CYLINDER
• PURPOSE
• 1. STORE FLUID
• 2. ACTIVATES THE BRAKES
• 3. PROVIDES OUTPUTS FOR 2 CIRCUITS....Why?

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Master Cylinder

• PRIMARY SIDE
• IS CLOSEST TO FIREWALL.
• SECONDARY SIDE
• IS FARTHEST FROM FIREWALL.
• DUAL MASTER CYLINDERS
• PRIMARY SIDE IS APPLIED BY MECHANICAL FORCE, THE
  SECONDARY SIDE IS APPLIED BY HYDRAULIC PRESSURE

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WHEEL CYLINDERS

• PURPOSE
• CONVERTS HYDRAULIC PRESSURE INTO MECHANICAL
  FORCE.
• Found Where?
• used in drum type systems to force the brake
  shoes against the drums.

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DOUBLE ENDED WHEEL CYLINDER
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Drum Brake Systems

• Function To slow wheel speed down by pushing
  shoes against the inside of a drum

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BRAKE SHOE DESIGN

• FRONT SHOE PRIMARY
• REAR SHOE SECONDARY.
• LEADING TYPE SHOE (PRIMARY) HAS SELF ENERGIZING
  OR SERVO ACTION.
• USES A SOLID ANCHOR BETWEEN SHOES.

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BRAKE DRUMS

• CONSTRUCTION
• CAST IRON
• CAST ALUMINUM WITH CAST IRON INSERT
• SOME DRUMS ARE EQUIPPED WITH FINS THESE ASSIST
  IN HEAT DISSIPATION.

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BRAKE DRUMS

• BRAKE DRUM SERVICING
• SCORED DRUM
• DRUM SHOWS VISIBLE SIGNS OF DAMAGE USUALLY DUE TO
  RIVETS IN SHOES CONTACTING DRUM.

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• METHODS OF TURNING A BRAKE DRUM
• Machine inside
• surface of drum
• Measure to make sure
• its still within Specs.
• after machining

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Disc Brake Systems

• Function
• Slows wheel speed by squeezing 2 brake pads
  against a disc (rotor)

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DISC BRAKE SYSTEMS

• ADVANTAGES
• 1. BETTER COOLING
• 2. LESS BRAKE FADE
• 3. EASIER TO MAINTAIN
• 4. SELF CLEANING
• 5. SELF ADJUSTING
• 6. NO ADJUSTMENTS REQUIRED
• (ON FRONT WHEEL SYSTEMS)

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DISADVANTAGES

• 1. OPEN TO ROAD SPLASH
• 2. HIGHER TEMPERATURE DEVELOPED IN CALIPER
  (HIGHER TEMPERATURE BRAKE FLUID IS NEEDED)
• 3. GREATER HYDRAULIC PRESSURE REQUIRED TO STOP
  VEHICLE
• 4. NO SELF ENERGIZING ACTION

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• BRAKE DISC OR ROTOR
• 1. CAST IRON
• 2. CAST ALUMINUM ALLOY
• TYPES
• 1. SOLID
• 2. VENTED- HAS AIR VENTS TO PROVIDE BETTER
  COOLING.
• SERVICE
• 1. CHECK FOR LATERAL RUNOUT, USING A DIAL
  INDICATOR
• 2. CHECK FOR SCORING/CORROSION
• 3. CHECK THICKNESS OF ROTOR USING A MICROMETER

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CALIPERS

• TYPES
• 1. FIXED TYPE - HAS PISTONS ON BOTH SIDES OF THE
  BRAKE DISC. TWO OR FOUR
• 2. FLOATING TYPE - HAS PISTON/S ON ONE SIDE OF
  THE ROTOR ONLY.

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• FIXED CALIPER
• FLOATING
• CALIPER

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OFF ON
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DIFFERENCE IN DISC BRAKE MASTER CYLINDER

• 1. NO RESIDUAL CHECK VALVE ON DISC BRAKE SIDE.
• 2. LARGER RESERVOIR ON DISC SIDE
• 3. LARGER BORE SIZE.
• 4. HIGHER BOILING POINT OF BRAKE FLUID.

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TYPES OF PADS

• 1. RIVETED
• 2. BONDED
• 3. BOLTED
• NOTE MAKE SURE ANTI- RATTLE CLIPS ARE INSTALLED
  AND RETAINER TABS ARE CLINCHED PROPERLY.CHECK M/F
  SPEC.

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RIVITED PADS
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BONDED PADS
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BRAKE FLUID

• 1. DO NOT REUSE BRAKE FLUID.
• 2. BRAKE FLUID MUST BE COMPATIBLE.
• CORROSIVE RESISTANT,HAVE A HIGH BOILING POINT(256
  DEGREES C),HAVE A LOW FREEZING POINT CONSISTENT
  VISCOSITY.
• S.A.E. RATINGS. SOCIETY OF AUTOMOTIVE ENGINEERS.
• DOT RATINGS 3,4,5 (5 IS SILCONE BASED AND NOT
  COMPATIBLE WITH 3 OR 4 DO NOT MIX)
• DRUM BRAKES
• MINIMUM BOILING POINT 374 F / 191 C
• DISC BRAKES
• MUST SAY FOR DISC BRAKES!
• MINIMUM BOILING POINT 475 F / 246 C

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BRAKE LINES

• 1. MUST BE DOUBLE WALL STEEL TUBE.
• NOTE DO NOT USE COPPER!
• 2. ALL ENDS MUST BE DOUBLE FLARED.
• 3. DO NOT USE COMPRESSION FITTINGS.
• 4. USE A TUBE BENDER.
• 5. FRONT OR REAR FLEX LINES MUST NOT BE CRACKED

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BLEEDING THE SYSTEM

• METHODS
• 1. MANUAL (TWO MAN OPERATION)
• A. PUMP BRAKE SLOWLY.
• B. DO NOT PUSH BRAKE PEDAL TO FLOOR.
  DAMAGE TO MASTER CYLINDER MAY RESULT.
• C. CHECK FLUID LEVEL FREQUENTLY TO PREVENT
  PUMPING MASTER CYLINDER DRY.
• 2. BLEEDER BALL
• THE BLEEDER BALL USES PRESSURIZED BRAKE FLUID TO
  FORCE AIR OUT OF SYSTEM.
• 3. SURGE BLEEDING
• THIS IS A COMBINATION OF 1 2
• 4. GRAVITY BLEEDING OPEN BLEEDER SCREWS AND LET
  GRAVITY DOTHE JOB.

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BRAKE BLEEDING
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CONTROL VALVESPRESSURE DIFFERENTIAL VALVE
SWITCH ASSEMBLY

• PURPOSE
• TO WARN DRIVER OF PRESSURE DROP ON EITHER SIDE OF
  THE SYSTEM.
• OPERATION
• PISTON WILL MOVE TO THE LOW PRESSURE SIDE OF THE
  SYSTEM CAUSING THE PIN IN THE SWITCH TO TOUCH THE
  RAMPS ON THE PISTON CLOSING THE CIRCUIT CAUSING
  THE LAMP IN THE DASH TO LIGHT.

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• PROPORTIONING VALVE
• LOCATION
• BETWEEN THE PRESSURE DIFFERENTIAL VALVE AND THE
  REAR WHEEL DRUM BRAKE SYSTEM.
• FUNCTION
• PROVIDES A BALANCED BRAKING ACTION BETWEEN FRONT
  DISC BRAKE AND REAR DRUM BRAKES UNDER A WIDE
  RANGE OF CONDITIONS.
• REDUCES REAR BRAKE HYDRAULIC PRESSURE TO BALANCE
  REAR BRAKE SELF-ENERGIZING ACTION AGAINST FRONT
  DISC BRAKE NON-SELF-ENERGIZING ACTION.
• PREVENTS REAR WHEEL LOCK-UP

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• METERING VALVE
• LOCATION
• BETWEEN THE PRESSURE DIFFERENTIAL VALVE AND THE
  FRONT DISC BRAKES CALIPERS.
• FUNCTION
• PREVENTS FRONT DISC BRAKES FROM DOING ALL THE
  BRAKING ACTION AT SLOW SPEED STOPS. HELPS TO
  INCREASE DISC PAD LIFE.
• 2. PREVENTS FRONT DISC BRAKES FROM APPLYING UNTIL
  MASTER CYLINDER PRESSURE REACHES 100-120 PSI TO
  OVER COME REAR DRUM BRAKE SHOE RETRACTION
  SPRINGS.
• 3. WHEN BLEEDING FRONT DISC BRAKES EQUIPPED WITH
  A METERING VALVE THE VALVE MAY HAVE TO BE HELD
  OPEN MANUALLY.

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• COMBINATION VALVE
• MAY CONTAIN A METERING VALVE, PROPORTIONING VALVE
  OR A PRESSURE DIFFERENTIAL VALVE.

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ABS Braking Systems

• Purpose to provide directional stability and
  steer ability during braking
• Types
• Integral combines the master cylinder, power
  booster and antilock system into one device
  (newer systems)
• Component uses existing master cylinder and
  power booster, then adds the necessary components
  to make the system anti lock (earlier systems)

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ABS

• Understanding ABS
• We need to know slippage ratio. 0 slippage
  ratio is a rolling wheel, 100 slippage is a
  skidding wheel.
• According to research a slippage ratio of 22
  provides the best braking possible and 8 still
  allows us to steer the vehicle
• Therefore ABS needs to work in a range of 8 to
  30
• Next we need to know the coefficient of friction,
  which changes with the road surface. Dry concrete
  provides the best value of 1.00, ice is the worst
  at a value of 0.10. These values are put into the
  computer to help control the system.

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ABS

• All systems use speed sensors. They are
  monitored by a computer, if the computer senses a
  sudden change in wheel speed at any wheel it
  starts to modulate the brake pressure to that
  wheel and keeps it within the braking (slippage)
  range.

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• 1.  Compressor
• 2.  Supply, Primary and Secondary Air Tanks
• 3.  Low Pressure Indicator Switch
• 4.  Safety Valve
• 5.  Drain Valves (Manual Automatic)
• 6.  Governor
• 7.  Single Check Valve
• 8.  Pressure Control Check Valve
• 9.  Air Gauge\
• 10.  Dual System Foot Brake Valve
• 11.  Quick Release Valve
• 12.  Service Brake Chamber
• 13.  Slack Adjuster
• 14.  Relay Valve
• 15.  Spring Parking Brake
• 16.  Quick Release and Double Check Valve
  Combination
• 17.  Stop Light Switch
• 18A.  Inversion Relay Valve
• 18B.  Spring Brake Control Valve

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