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Braking System OperationBraking System Operation

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Slideshow ContentsSlideshow Contents

• Part 1: base braking systemPart 1: base braking system slides 1-21slides 1-21

• Part 2: anti-lock braking systemsPart 2: anti-lock braking systems slides 22-31slides 22-31

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• braking force is not 50% front & 50% rearbraking force is not 50% front & 50% rear

• front brakes can apply up to 90% of the braking powerfront brakes can apply up to 90% of the braking power

this depends partly on whether vehicle is front or rear drive this depends partly on whether vehicle is front or rear drive (weight distribution)(weight distribution)

this is why front brakes may have to be replaced 4 or 5 times this is why front brakes may have to be replaced 4 or 5 times before the rear brakes need replacementbefore the rear brakes need replacement

Weight Distribution During Braking…Weight Distribution During Braking…

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Weight Distribution During Braking…Weight Distribution During Braking…

Hydraulic SystemsHydraulic Systems

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Braking System ComponentsBraking System Components

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Master CylinderMaster Cylinder

• converts pedal movement to hydraulic pressureconverts pedal movement to hydraulic pressure

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Master Cylinder ActionMaster Cylinder Action

• applied position (pushing on brake pedal)… applied position (pushing on brake pedal)…

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Master Cylinder OperationMaster Cylinder Operation

• brakes being appliedbrakes being applied

• brake pedal releasedbrake pedal released

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Caliper DesignsCaliper Designs

• fixed caliperfixed caliper pistons on both sides of the brake discpistons on both sides of the brake disc

caliper can have 2 or 4 pistonscaliper can have 2 or 4 pistons there are some 8 piston versions for race applicationsthere are some 8 piston versions for race applications

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Caliper DesignCaliper Design

• floating caliperfloating caliper uses 1 or 2 uses 1 or 2 pistons on one sidepistons on one side of the caliper of the caliper caliper body slides (in reaction to the piston movement)caliper body slides (in reaction to the piston movement) outer brake pad rubs on the outside of the discouter brake pad rubs on the outside of the disc

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Brake Pad RetractionBrake Pad Retraction

• flexing of the caliper’s square cut o-ring causes piston to retract when the brake pedal is flexing of the caliper’s square cut o-ring causes piston to retract when the brake pedal is releasedreleased no return springs requiredno return springs required

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Drum BrakesDrum Brakes

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Self Energized, Non-Servo (Leading-Trailing) Drum BrakesSelf Energized, Non-Servo (Leading-Trailing) Drum Brakes

• bottom of the brake shoes mount to a solid anchorbottom of the brake shoes mount to a solid anchor• leading (front) brake shoe is self-energizedleading (front) brake shoe is self-energized

drum rotation increases braking forcedrum rotation increases braking force front (leading) brake shoe is wedged tightly against the drumfront (leading) brake shoe is wedged tightly against the drum

• brake shoes are equal lengthbrake shoes are equal length• front (leading) brake shoe maybe thicker than the rear (trailing)front (leading) brake shoe maybe thicker than the rear (trailing)• used on many front wheel drive vehiclesused on many front wheel drive vehicles

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Self Energized, “Dual-Servo” Drum BrakesSelf Energized, “Dual-Servo” Drum Brakes

• one shoe “serves” the other to increase application forceone shoe “serves” the other to increase application force

• note how the bottom of the brake shoes are note how the bottom of the brake shoes are notnot mounted on a fixed anchor mounted on a fixed anchor

• the brake shoes can pivot or rotate with the drumthe brake shoes can pivot or rotate with the drum

• front (primary) shoe helps increase pressure on rear (secondary) shoe front (primary) shoe helps increase pressure on rear (secondary) shoe

this is referred to as servo actionthis is referred to as servo action

• brake shoes are different lengths (longer on back side {secondary shoe})brake shoes are different lengths (longer on back side {secondary shoe})

• drum rotation energizes both brake shoesdrum rotation energizes both brake shoes

• used on many rear wheel drive vehiclesused on many rear wheel drive vehicles

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Hydraulic Line ConnectionsHydraulic Line Connections

• single piston master cylindersingle piston master cylinder

used until 1967used until 1967

• tandem split (fig. 11a)tandem split (fig. 11a)

used on rear drive vehiclesused on rear drive vehicles

• diagonal split (fig. 11b)diagonal split (fig. 11b)

used on front drive vehiclesused on front drive vehicles

Fig. 11a Fig 11b

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Brake Hydraulic Control ValvesBrake Hydraulic Control Valves

1)1) metering valvemetering valve: delays front brake application until rear brakes have overcome spring : delays front brake application until rear brakes have overcome spring

tension tension

used used on disc/drum system onlyon disc/drum system only

used mainly onused mainly on rear wheel drive vehicles rear wheel drive vehicles

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Brake Hydraulic Control ValvesBrake Hydraulic Control Valves

• proportioning valveproportioning valve: limits hydraulic pressure to rear brakes under : limits hydraulic pressure to rear brakes under hard brakinghard braking to to

prevent wheel lock-upprevent wheel lock-up

• has no effect during light to moderate stops has no effect during light to moderate stops

Proportioning Valve Operation

light to moderate braking:• master cylinder pressure acts on both sides of the piston• pressure to front & rear brakes is equal

heavy braking:• pressure on large area of piston forces piston to left• this blocks pressure to rear brakes• piston will cycle back and forth only allowing a percentage of front brake pressure to the rear

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Brake Hydraulic Control ValvesBrake Hydraulic Control Valves

Pressure Differential switch turns on a warning light if hydraulic pressure in one circuit is lost due to a leak

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Parking Brakes with Rear DrumsParking Brakes with Rear Drums

• mechanical cable actuates the brake shoes (on rear wheels)mechanical cable actuates the brake shoes (on rear wheels)

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Parking Brakes on Rear DiscsParking Brakes on Rear Discs

• 2 methods of applying the e-brake on vehicles that use rear disc 2 methods of applying the e-brake on vehicles that use rear disc brakes…brakes…

1) cable moves caliper piston out

2) cable pushes out mini brake shoes against the inside of the brake rotor