Braking Systems For Automobiles

Dr.S.John Alexis

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Basics of Hydraulics

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Hydraulic Action in the Wheel Cylinder

Advantage by Hydraulics

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PURPOSE OF BRAKING SYSTEM• Stop the vehicle by converting the kinetic energy of

the vehicle to heat energy.• Heat energy is created in the brakes by friction.• Friction is created between a moving and a non-

moving surface at each wheel to generate the heat.• Disc and drum brakes are the most common type of

braking systems used.

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Factors Effecting Braking*

• Number of wheels braking.

• Weight of vehicle.• Type of friction

material.• Surface area of friction

material.• Size or discs or drums

• Tire traction.• Road surface.• Load transfer.• Incline or decline of

road. (gravity)• Engine braking.• Pressure applied

Disc and Drum Brakes• Disc brakes are found on almost all vehicles now.• Older cars and trucks had a combination of disc and

drum brakes.• At one time vehicles came with drum brakes only

(1970 and older)

Types of Linings• Asbestos- these have phased out, very hazardous to

breath the dust.• Organic- mixture of asbestos and organic materials

with a resin binder• Semi-metallic- organic mixed with metal shavings,

last longer and very good at dissipating heat.• Ceramic – low dust output, provide exceptional

braking performance • Carbon/Kevlar- Motor sports application, not used

on road vehicles because of cost and they take time to warm up.

• This is why we don’t use a bow gun to clean brakes or brake parts (asbestos is hazardous in the airborne form)

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Types of Braking Systems• Service brakes. It’s the

primary braking system using a the pedal connected to a hydraulic system causing it to operate.

• Parking brakes. It’s mechanically applied by a lever or pedal.

Drum Brake System

Drum Parts

Hardware Backing plate

Drum

Wheel Cylinder

Adjusting Screw

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Drum Brake ActionAdjust by driving in reverse and braking

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DRUM BRAKES• Wheel Cylinder

.Backing Plate

.Secondary Brake Shoe

Upper Return Spring

Parking Brake Lever

Primary Brake Shoe

Piston

Adjuster

Anchor Pin

.Lower Return Spring

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HYDRAULIC SYSTEM

• Brake pedal assembly• Power booster• Master cylinder• Proportioning valve• Metering valve• Warning light valve• Lines• Calipers• Wheel cylinders

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Master Cylinder

ToFront Brakes

To Rear Brakes

Master Cylinder

Reservoirs

PowerBooster

Vacuum Line

Brake Pedal

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Disc Brake Rotor Rotor

PadsCaliperPistonBrake LineBleeder screwThrough Bolts

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Caliper

• Boot• Piston• Seal• Caliper Housing• Bleed Screw• O-Ring• Bushing• Bolts

Sliding Caliper• Applies pressure to

two pads on opposite sides of rotor

• Caliper– Sliding – Fixed

• Friction Material exposed to air

Fixed Caliper

• Applies two pistons to opposite sides of rotor

• Caliper stays stationary

• Disc Brakes require higher hydraulic pressure

Braking Dynamics• Weight Transfer• Weight Distribution• Braking Power• Friction Efficiency

– Brake to Wheel– Wheel to Road Surface

• Traction Efficiency– Skidding

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Brake Lines

• Brake lines are steel tubing with copper and lead coatings to prevent rust and corrosion.

• As the brake pedal is depressed, it moves pistons within the master cylinder and forcing hydraulic brake fluid

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Brake Lines

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ABS• Wheel locks up-

reduces power to that wheel

• Pulsates brakes if sliding

• Pulsates brakes on hard braking

• Stops vehicle under control

• NOT faster