Beginner's Auto Maintenance & Repair



Brakes offer a way to slow the momentum of a vehicle for better control and safety on the road. A brake system uses the hydraulic advantage to apply force to a friction material that generates heat. A moving vehicle has kinetic energy. Brakes convert kinetic energy into heat energy.

Disc brakes and drum brakes are two types of brakes. The main differences are the shapes of the brakes and their friction material. Friction material provides the buffer that prevents metal from grinding when applying brakes.

Disc brakes have a rotor (disc) for each wheel, and brake pads are the friction material. A brake caliper applies force to a brake pad, which presses it against the rotor when it is used. It generates heat and stops the vehicle.


A disc brake. The rotor is the shiny gold-colored disc and the caliper is red. The black piece between thecaliper and the rotor is the pad.
A disc brake. The rotor is the shiny gold-colored disc and the caliper is red. The black piece between the caliper and the rotor is the pad.


Disc brake pads. Theyre red in this image. They can be any color.
Disc brake pads. Theyre red in this image. They can be any color.


Drum brakes are shaped like a drum, and brake shoes are made of friction material. A wheel cylinder applies pressure to a brake shoe with a friction lining. Think of a circle within a circle. A hydraulic device expands the shape of the shoes to press against the drum. It generates heat and stops the vehicle.


Illustration of a drum brake
Illustration of a drum brake


Drum brake shoes (violet color) and linings
Drum brake shoes (violet color) and linings


The master cylinder is used to apply force to the brake calipers and wheel cylinders. The wheel cylinders (used in drum brakes) and the brake calipers (used in disc brakes) are hydraulic slave cylinders.

Anti-lock brakes have complex electrical and hydraulic components to avoid skidding wheels in a panic stop or poor traction conditions. The anti-lock brakes (ABS) use signals from each wheel speed sensor to determine if one wheel is

Stopping faster than any of the others. If this occurs, the ABS control module (a computer) will signal the ABS hydraulic control unit to isolate that wheel, release brake pressure, and then pulsates the brake pressure to maintain equal speeds for all four
wheels. It helps avoid skidding and maintains maneuverability during a panic stop.

How to Check the Brake System:

The mechanic often checks the brake system during routine oil changes and maintenance. It can also be checked at home. Consult the service manual of the specific make and model about checking the brakes and finding the locations of each part of the brake system. Follow these steps to prevent the brake system:

  • Start under the hood.
  • Check the brake master cylinder for leaks.
  • Check the level and condition of the brake fluid
  • Inspect all lines and the anti-lock brake module for leaks or loose, damaged connectors.
  • Raise the vehicle and support it securely on a lift or jack stands
  • Remove all four wheels
  • If the vehicle has drum brakes, then remove the drums.
  • Inspect all brake lines and hoses for signs of leaking or cracking
  • Inspect the caliper hardware and dust boots for damage
  • Inspect the caliper (or wheel cylinders) for brake fluid leaking
  • Inspect the rotors for smoothness.
  • Check the thickness of all the brake pads.

Suppose there is any variation in the brake pad (or shoe) thickness between the driver and passenger sides. There may be an adjustment problem, a defective caliper, or other hardware in that case. Usually, the front brakes wear faster since the front brakes are responsible for about 80% of the stopping. There is no blanket measurement for brake pad thickness since the thickness of new pads can vary by the make and model of the vehicle. A few millimeters could appear brand new in one car but indicate pad replacement in another. The original thickness can be found in the service manual for the vehicle