BRAKE SYSTEMS

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

How do Brakes Work Drivers need to be able to activate brakes as required This is accomplished by foot pedals or hand levers.

How do Brakes Work?

4 TYPES OF BRAKING SYSTEMS 1. HYDRAULIC 2. COMPRESSED AIR 3. MECHANICAL 4. ELECTRICAL

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

Force Increase Brake force is increased by 2 methods: 1) Hydraulic Advantage 2) Mechanical Advantage

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

Levers

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

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

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

Master Cylinder PRIMARY SIDE: SECONDARY SIDE: DUAL MASTER CYLINDERS: 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

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

DOUBLE ENDED WHEEL CYLINDER

Drum Brake Systems Function: To slow wheel speed down by pushing shoes against the inside of a drum

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.

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

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

METHODS OF TURNING A BRAKE DRUM: Machine inside surface of drum Measure to make sure it’s still within Specs. after machining

Disc Brake Systems Function: Slows wheel speed by squeezing 2 brake pads against a disc (rotor)

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)

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

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

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.

FIXED CALIPER FLOATING CALIPER

OFF ON

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.

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.

RIVITED PADS

BONDED PADS

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

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

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.

BRAKE BLEEDING

CONTROL VALVES: PRESSURE 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.

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

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.

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

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)

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.

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.

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 19.  Air Dryer 20.  ABS Electronic Control Unit, Modulator Valves, Sensors and Tooth Rings 20A.  Front Axle Valve Package 20B.  Rear Axle Valve Package 21.  Two-Line Tractor Protection Valve (Non-Automatic Type) 22.  Hand Control Valve - Trailer Service Brakes 23.  Double Check Valve 24.  Double Check Valve 25.  Manifold Dash Valve