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Home >   How To >   How to Repair Brake System >   What is a Brake Disc?

What is a Brake Disc?

The brake disc is the component against which the brake pads clamp on to slow or stop the wheels. The friction between the disc and pads causes the requisite braking action in the wheels. Other components involved in braking include the master cylinder and caliper. The disc is a circular component with a machined surface on both of its sides. The brake disc is held in place by two set screws and a center nut. In some automobiles, the disc is simply attached to the wheel. The disc is usually made of cast iron or ceramic.





Some high-performance applications have specialized discs to handle the large amount of heat generated due to friction: Some discs have holes drilled in them so that the heat generated can be dissipated via the holes easily. In addition, when the car drives in rainy conditions, the holes in the rotor can quickly drain the water. Drilled discs are widely used in racing automobiles. Some discs employ carved slots on their surface instead of holes to easily dissipate the heat. Some recent brake disc rotor types have both holes and slots on their surface to provide an efficient braking performance.


Disc brake systems are superior to drum brake systems in various ways. The disc brakes require no adjustments to the rotor when they are installed. A further benefit of disc brakes is that heat gets easily dissipated compared to drum brakes.



Brake Disc



Problems in a Brake Disc


  • Generally, the brake calipers are the ones that wear out quicker than brake discs. However, the brake rotor, in the long run, can become thin and fail to dissipate the heat. This results in a poor braking performance.
  • Sometimes, the brake disc may develop warps, failing to provide an efficient braking.
  • The brake pads can lose their friction material over time, resulting in a metal-to-metal contact between the pad and rotor. This will also cause the brake disc to go bad.
  • The brake disc in vehicles which have not been driven for a long time can develop rust. This can be rectified by machining the rotor.
  • A warped brake disc rotor can also affect the anti-lock braking system.
  • The brake disc can fail due to brake-fluid leaks. This can cause the fluid to coat the surface of the rotor.


Symptoms of a Bad Brake Disc


  • A grinding or squealing noise while braking is often a symptom of bad brake discs. However, the grinding noise may also be emitted when the brake pedal is not pressed and can get louder while braking. This also indicates a bad disc rotor.
  • A defective brake disc can cause the vehicle to vibrate or lurch when the brake pedal is pressed. This condition is often called a "shimmy".
  • A bad brake disc an also cause your steering wheel to vibrate even at normal speeds.
  • Pulsating brakes are also a common indication of damaged brake rotors.
  • A disc rotor that has completely gone bad can cause your vehicle to stop roughly. On the contrary, a worn-out rotor can also increase the stopping distance of your vehicle.
  • Other problems due to a bad brake disc include loss of wheel torque and diminished steering response.
  • If a failed brake rotor is not attended at the earliest, it can wreak havoc in the entire braking system and performance.




As with all auto parts, the brake discs also need to be inspected regularly. Cleaning the rotors with a brake cleaning fluid spray is also critical to keep foreign particles and brake dust out, and prolong the lifetime of the rotor.


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