1. Braking System Operation

2. Slideshow Contents Part 1: base braking system slides 1-21
Part 2: anti-lock braking systems
slides 22-31

3. Weight Distribution During Braking…
braking force is not 50% front & 50% rear
front brakes can apply up to 90% of the braking power
this depends partly on whether vehicle is front or rear drive (weight distribution)
this is why front brakes may have to be replaced 4 or 5 times before the rear brakes need replacement

4. Weight Distribution During Braking…

5. Hydraulic Systems

6. Braking System Components

7. Master Cylinder
converts pedal movement to hydraulic pressure

8. Master Cylinder Action
applied position (pushing on brake pedal)…

9. Master Cylinder Operation
brakes being applied
brake pedal released

10. Caliper Designs fixed caliper pistons on both sides of the brake disc
caliper can have 2 or 4 pistons
there are some 8 piston versions for race applications
little/no flex in the caliper body during heavy braking
this results in a firmer brake pedal and increased braking power
more expensive to manufacture and repair

11. Caliper Design floating caliper
uses 1 or 2 pistons on one side of the caliper
caliper body slides (in reaction to the piston movement)
outer brake pad rubs on the outside of the disc

12. Brake Pad Retraction
flexing of the caliper’s square cut o-ring causes piston to retract when the brake pedal is released
no return springs required

13. Drum Brakes

14. Self Energized, Non-Servo (Leading-Trailing) Drum Brakes
bottom of the brake shoes mount to a solid anchor
leading (front) brake shoe is self-energized
drum rotation increases braking force
front (leading) brake shoe is wedged tightly against the drum
brake shoes are equal length
front (leading) brake shoe maybe thicker than the rear (trailing)
used on many front wheel drive vehicles

15. Self Energized, “Dual-Servo” Drum Brakes
one shoe “serves” the other to increase application force
note how the bottom of the brake shoes are not mounted on a fixed anchor
the brake shoes can pivot or rotate with the drum
front (primary) shoe helps increase pressure on rear (secondary) shoe
this is referred to as servo action
brake shoes are different lengths (longer on back side {secondary shoe})
drum rotation energizes both brake shoes
used on many rear wheel drive vehicles
when reversing the vehicle, the servo action is reversed - secondary shoe assists the primary shoe – hence the name “dual-servo”
primary shoe provides ≈ 30% of the stopping power
secondary shoe, which is “served” by the primary shoe provides ≈ 70% of the braking force

16. Hydraulic Line Connections
single piston master cylinder
used until 1967
tandem split (fig. 11a)
used on rear drive vehicles
diagonal split (fig. 11b)
used on front drive vehicles
Fig. 11a
Fig 11b

17. Brake Hydraulic Control Valves
metering valve: delays front brake application until rear brakes have overcome spring tension
used on disc/drum system only
used mainly on rear wheel drive vehicles

18. Brake Hydraulic Control Valves
proportioning valve: limits hydraulic pressure to rear brakes under hard braking to prevent wheel lock-up
has no effect during light to moderate stops

19. Proportioning Valve Operation
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
light to moderate braking:
master cylinder pressure acts on
both sides of the piston
pressure to front & rear brakes is equal

20. Brake Hydraulic Control Valves
Pressure Differential switch turns on a warning light
if hydraulic pressure in one circuit is lost due to a leak

21. Parking Brakes with Rear Drums
mechanical cable actuates the brake shoes (on rear wheels)

22. Parking Brakes on Rear Discs
2 methods of applying the e-brake on vehicles that use rear disc brakes…
1) cable moves caliper piston out
2) cable pushes out mini brake shoes
against the inside of the brake rotor