Brake Systems Study Guide

Brake System Principles

  • Allows driver to safely and efficiently slow/stop vehicle.
  • Converts kinetic energy of motion into heat via brakes.
  • Modern systems incorporate mechanical, hydraulic, electronic components.

Types of Energy

  • Kinetic Energy: Energy of motion.
  • Potential Energy: Stored energy in non-moving objects.

Friction

  • Friction: Resistance between two moving objects, crucial for braking.
  • High heat can be generated (up to 500°F).
  • Coefficient of Friction (CoF) determines friction and heat generation:
    • Static Friction: Between nonmoving parts.
    • Kinetic Friction: Between moving parts.

Brake Fade

  • Brake Fade: Reduced effectiveness of brakes due to overheating.
  • Types:
    • Mechanical: Drum overheating expands, increasing pedal travel.
    • Lining: Pad material overheats, reducing CoF.
    • Gas: Thin layer of gas acts as lubricant under extreme braking.
    • Water: Water intrusion can reduce braking effectiveness.

Heat Dissipation

  • Brake systems must dissipate heat quickly to prevent damage (boiling fluid, reduced performance).

Brake System Types

  • Service Brakes (Primary): Disc and drum brakes.
  • Parking Brakes (Secondary): Not emergency brakes, smaller designed for holding vehicle.

Brake Pedal Mechanics

  • Utilizes leverage, hydraulics, and electronics.
  • Pushrod connected below pivot point applies increased force when brakes are applied.

Brake Fluid

  • Specified by DOT numbers: 3, 4, 5, 5.1 (different properties).
  • Toxic and can damage painted surfaces; should be kept clean and properly stored.

Hydraulic Brake System Components

  • Components include:
    • Master cylinder, brake lines/hoses, valves, calipers, wheel cylinders.
  • Dual pistons in master cylinders prevent loss of braking.

Metering and Proportioning Valves

  • Metering Valve: Controls pressure to front disc brakes.
  • Proportioning Valve: Prevents rear drum brake lock-up during heavy braking.

Brake Pull Diagnostics

  • Pull to left or right indicates potential problems with calipers or hoses, requiring inspection.

Disc Brake Systems

  • Common in modern vehicles, advantages include resistance to fade, but require power assist due to higher force needed.

Brake Calipers and Components

  • Several configurations (fixed, floating) for various applications.
  • Responsible for applying brake pads against the rotor.

Brake Pads and Wear Indication

  • Made from various materials (organic, semi-metallic, ceramic).
  • Indicators for wear include grooves, acoustic indicators, and wear sensors.

Parking Brakes

  • Mechanical brake system separate from hydraulic, ensures function if hydraulic pressure fails.
  • Integrated or electronic designs increasingly used in newer models.
  • Diagnostics include checking cable function and adjustment to ensure effectiveness.

Hybrid Brakes

  • Regenerative braking technology recovers energy to charge batteries, significantly reducing wear on service brakes.