1. Brake System Fundamentals
Walla Walla Community College
Automotive Technology

2. Typical System (No ABS)

3. Typical Layout of System (with ABS)

4. Brake Pedal Design Advantage by Leverage
First Mechanical Advantage is Driver’s foot
Length of Lever determines force applied
Uses Fulcrum
Pedal Ratio 10
5:1
2.5 inches
0.5 inch 2 5

5. Advantage by Hydraulics

6. Components

7. Drum Brake System

8. Disc Brake Caliper Assembly

9. Sliding Caliper
Applies pressure to two pads on opposite sides of rotor
Caliper
Sliding
Fixed
Friction Material exposed to air

10. Fixed Caliper Applies two pistons to opposite sides of rotor
Caliper stays stationary
Disc Brakes require higher hydraulic pressure

11. Master Cylinder

12. Brake Plumbing Rigid steel brake lines are double wall
Flexible hoses connect rigid lines on vehicle to each wheel
Transmits hydraulic fluid to each wheel

13. Pressure Control Valves
All systems use one or more valves

14. Wheel Cylinder Wheel cylinder or caliper pistons are “slave cylinders”
Change hydraulic pressure back into mechanical force
Can use one or two cylinders at each wheel

15. Power Assist Increases force of driver’s foot

16. Cable Parking Brake
Parking or “Emergency” Brake

17. Parking Brake Systems Foot or Hand Brake Are cable controlled
Several Styles
As shown
Drum in hat
Driveline

18. Brake System Energy

19. Brake System Principles
Kinetic Energy
Mass
Weight
Speed
Inertia and Momentum

20. Friction Principles Friction changes kinetic energy into
Kinetic and Static Friction
Friction and Pressure
Friction and Surface Area
Coefficient of Friction
Brake Fade
Friction changes
kinetic energy into
heat (thermal) energy.

21. Brake Friction Materials
Five Characteristics
Resist Fading with increased temp
Resist fading when wet
Recover quickly
Wear gradually
Quiet
Bonded or Riveted

22. Braking Dynamics Weight Transfer Weight Distribution Braking Power
Friction Efficiency
Brake to Wheel
Wheel to Road Surface
Traction Efficiency
Skidding

23. Hydraulic Principles Fluids cannot be compressed
Fluids can transmit Movement
Acts “Like a steel rod” in a closed container
Master cylinder transmits fluid to wheel cylinder or caliper piston bore.
Fluids can transmit and increase force
Force
Pressure
Area

24. The area of the piston is determined by using the formula:
3.14 X R2

25. The amount force is calculated by multiplying the pressure times the area
P X A = Force

26. Hydraulics - it’s how the pressure is multiplied and transferred

27. Hydraulic pressure is distributed equally in all directions

28. The pressure that is applied at piston A is the same as what is applied to piston B

29. The hydraulic pressure is the same, but the applied force can be changed by changing the piston size.

30. You can’t have something for nothing

31. The caliper piston needs more applied force for multiple reasons