1. 1 Braking System Operation Roger Bortignon

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

3. 3 braking force is not 50% front & 50% rearbraking force is not 50% front & 50% rear front brakes can apply up to 80% of the braking powerfront brakes can apply up to 80% 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 Weight Distribution During Braking…

4. 4

5. 5 Braking System Components

6. 6 Master Cylinder converts pedal movement to hydraulic pressureconverts pedal movement to hydraulic pressure

7. 7 Master Cylinder Action applied position (pushing on brake pedal)…applied position (pushing on brake pedal)…

8. 8 Master Cylinder Operation brakes being appliedbrakes being applied brake pedal releasedbrake pedal released

9. 9 Caliper Designs fixed caliperfixed 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

10. 10 Caliper Design floating caliperfloating 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

11. 11 Brake Pad Retraction flexing of the caliper’s square cut o-ring causes piston to retract when the brake pedal is releasedflexing of the caliper’s square cut o-ring causes piston to retract when the brake pedal is released  no return springs required

12. 12 Drum Brakes

13. 13 Self 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 force  front (leading) brake shoe is wedged tightly against the drum brake shoes are equal lengthbrake shoes are equal length front (leading) brake shoe may be thicker than the rear (trailing)front (leading) brake shoe may be thicker than the rear (trailing) used on the rear of many front wheel drive vehiclesused on the rear of many front wheel drive vehicles

14. 14 Self 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 not mounted on a fixed anchornote how the bottom of the brake shoes are not 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) shoefront (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})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

15. 15 Hydraulic Line Connections single piston master cylindersingle piston master cylinder  used until 1967 tandem split (fig. 11a)tandem split (fig. 11a)  used on rear drive vehicles diagonal split (fig. 11b)diagonal split (fig. 11b)  used on front drive vehicles Fig. 11a Fig 11b

16. 16 Brake Hydraulic Control Valves 1)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

17. 17 Brake Hydraulic Control Valves proportioning valve: limits hydraulic pressure to rear brakes under hard braking to prevent wheel lock-upproportioning valve: limits hydraulic pressure to rear brakes under hard braking to prevent wheel lock-up has no effect during light to moderate stopshas no effect during light to moderate stops

18. Proportioning Valve Operation light to moderate braking: master cylinder pressure acts on both sides of the green 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

19. 19 Brake Hydraulic Control Valves Pressure Differential switch turns on a warning light if hydraulic pressure in one circuit is lost due to a leak...

20. 20 Parking Brakes with Rear Drums mechanical cable actuates the brake shoes (on rear wheels)mechanical cable actuates the brake shoes (on rear wheels)

21. 21 Parking Brakes on Rear Discs 2 methods of applying the e-brake on vehicles that use rear disc brakes…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

22. 22 Anti-lock Brake Systems ABS

23. 23ABS designed to prevent wheel lock-up to minimize stopping distance & help maintain steering controldesigned to prevent wheel lock-up to minimize stopping distance & help maintain steering control  by preventing wheel lock-up, tires will maintain traction with road surface can also used on motorcycles and even trucks & buses with air brakescan also used on motorcycles and even trucks & buses with air brakes

24. 24 ABS Components

25. 25 How Many Channels? a channel describes a hydraulic brake line that is capable of being controlled by the ABS modulea channel describes a hydraulic brake line that is capable of being controlled by the ABS module

26. 26 Wheel Speed Sensor wheel speed sensor is a magnetic impulse sensorwheel speed sensor is a magnetic impulse sensor  works like a crankshaft position sensor creates an AC voltage signal as the tone ring rotates with the wheelcreates an AC voltage signal as the tone ring rotates with the wheel the AC voltage signal frequency changes as the wheel speed changesthe AC voltage signal frequency changes as the wheel speed changes

27. 27 AC voltage ripple frequency will change with wheel speed changesAC voltage ripple frequency will change with wheel speed changes

28. 28 Modulating Brake Fluid Pressure Electronic Brake Control Modulator EBCMElectronic Brake Control Modulator EBCM EBCM-activated solenoids modulate brake fluid pressureEBCM-activated solenoids modulate brake fluid pressure the solenoid valves can (while driver is stepping on pedal) either…the solenoid valves can (while driver is stepping on pedal) either…  hold (maintain) pressure  dump (release) pressure  increase pressure  these solenoids can cycle the brakes 15 times/second Hold PressureDump PressureIncrease Pressure proportioning valve is no longer needed!

29. 29 ABS Modulator may be attached to the master cylindermay be attached to the master cylinder  integral ABS may be mounted separate from the master cylindermay be mounted separate from the master cylinder  non-integral ABS

30. 30 schematic of brake lines and ABS components…schematic of brake lines and ABS components…