Auto 1

1. BRAKE SYSTEM
OVERVIEW
1

2. VACUUM ASSIST BOOSTER
2

3. THE MASTER CYLINDER
3

4. BRAKE FLUID AND BRAKE CLEANERS
Brake fluid comes in several types
 DOT 3, 4, 5, 5.1
 Most common today is Polyglycol DOT 3 and DOT 4
 Both collect water because they are Hydroscopic
 DOT 3 Min boil point 401 dry 284 wet, can absorb 3% water by
volume
 DOT 4 Min boil point 446 dry 311 wet
 DOT 5 Min boil point 500 dry 356 wet
 DOT 5.1 Min. boil point 518 dry 374 wet
 Silicone should not be mixed with 3 or 4
NEVER MIX PETROLEUM BASED
PRODUCTS WITH BRAKE
SYSTEMS!
4

5. FIXED CALIPER
Caliper remains stationary as pistons on each side
clamp the rotor
5

6. SINGLE PISTON CALIPER
Caliper slides as the piston moves in to clamp the
brake pads against the rotor
6

7. BRAKE CALIPER ASSEMBLY
7

8. CALIPER COMPONENTS
Piston seal
 prevents fluid leakage between the piston and the cylinder
 helps pull the piston back into the cylinder when the brakes are
not applied
Boot
 prevents road dirt and water entry
Bleeder screw
 allows air to be removed from the system
8

9. CALIPER OPERATION
When the brakes are applied, brake fluid flows into
the caliper cylinder
Fluid pressure pushes the piston outward, forcing
the brake pads into the rotor
When the brakes are released, the stretched piston
seal pulls the piston back into the bore, as fluid
pressure drops
9

10. CALIPER OPERATION
Brakes applied Brakes released
10

11. WHEEL CYLINDER INNARDS
11

12. DISC BRAKE PADS
Riveted or Bonded Pads
Linings
 Organic
 Semi-Metallic
 Ceramic
Cars typically use Semi-Metallic front and Organic
rear
12

13. NON-ASBESTOS ORGANIC
• Sometimes listed as organic or NAO
• Contains non-asbestos fibers, such as glass,
rubber, carbon, and Kevlar, with filler materials
and high-temperature resins
• These pads are softer and create less noise
• Wear faster and create more dust
13

14. SEMI-METALLIC PADS
• Containing about 30 to 65 percent metal
• Typically includes chopped steel wool or wire,
iron powder, copper or graphite mixed with
inorganic fillers, and friction modifiers as
bonding agent
• More durable and have excellent heat transfer
• Wear rotors faster
• Noisy
• May not perform as well under low-temperature
conditions
14

15. LOW-METALLIC
• Organic formula mixed with small amounts 10-
30% of copper or steel to help with heat transfer
and provide better braking
• With the added metal, there is more brake dust
and they may be slightly noisier
15

16. CERAMIC
• Composed of ceramic fibers, nonferrous filler
materials, bonding agents, and possibly small
amounts of metal
• Lighter in color and more expensive than other
brake pads
• Ceramic pads are cleaner and quieter
• Offer excellent braking characteristics hot and
cold
• Low rotor wear
16

17. PAD HARDWARE
Anti-rattle clips
Keep the brake pads from vibrating and rattling
Prevents click noise on forward and reverse braking
Brake pad shims
Can be single or multiple shims
Pad wear sensor
Metal tab on the brake pad
Emits a loud squeal when it scrapes against the brake
disc when the lining has worn too thin (approx. 1mm or
2/32”)
17

18. ELECTRONIC PAD WEAR SENSOR
18

19. BRAKE PAD WEAR
19

20. BRAKE DISC (ROTOR)
• Uses friction from the brake pads to slow or
stop wheel rotation
• Normally made of cast iron
• Can be Carbon Fiber (racer with bottomless
wallet)
• Constructed as part of the hub, or a separate
unit
• May be solid, cross drilled or a ventilated rib
construction
20

21. ROTOR DIAGNOSIS
• Check parallelism
• Thickness
• Lateral Run-out
• Cracks and hot spots
24

22. ROTOR HOT SPOTS
25