Mechanics

Brake Rotor

How to Replace a Brake Rotor
A brake rotor is designed to utilize brake pressure provided by the brake system to stop the car. This brake rotor utilizes friction and heat to convert momentum into stopping power. Brake pads ride against either side of the brake rotor and are held in place by the brake caliper. A brake caliper is typically mounted to the spindle or backing plate. There are two basic designs of brake caliper mounting, fixed and floating. A fixed position brake caliper is bolted to the spindle and is not allowed to move. The brake master cylinder supplies the hydraulic pressure to activate the brake pads. 

Brake rotors can either be solid or ventilated (image below) depending on the application design. Most brake rotors can be re-machined, there is a minimum thickness measurement requirement designed to uphold performance specifications. Once a rotor reached this minimum measurement the rotor must be discarded. A brake rotor is only capable of holding a specific amount of heat, once this level is reached the brake rotor will not hold additional heat causing brake fade. Brake fade is a condition that will hinder the brake performance until the brake rotor has cooled. If a brake rotor is subjected to prolonged over heat conditions it can destroy the rotor by crystallizing the metal the rotor is constructed from.

Brake Rotor
Brake Rotor (appearance will vary)

When brakes pads wear out it will cause the rotor to contact the brake pad backing plate. This backing plate is made of metal and will destroy the brake rotor (image below). If this condition is allowed to continue brake operation could fail completely. When replacing a brake rotor always insist on high quality replacement brake rotors. If cheap replacement parts are used it can cause the brake rotor to squeak and prematurely warp due to heat. If you are replacing brake pads and not brake rotors a newly machined surface is recommended before installing new brake pads to ensure proper brake operation. If this operation is not performed it can cause the brake pedal to pulsate or the brakes to squeak.

Broken Brake Rotor
Broken Brake Rotor

Replacing a Brake Rotor Outline

  • Loosen but (Do Not Remove) the lug nuts of the wheel to be serviced
  • Support car in a safe position high enough to remove the brake rotor and pads
  • Remove the lug nuts and wheel
  • Use a pry bar to force the caliper piston into the caliper
  • Loosen appropriate nuts and bolts to remove the brake caliper
  • Remove the caliper, brake pads and rotor
  • Clean all rotor and brake pad mounting surfaces
  • Install new brake pads and rotors (or re-machined rotors) and reassemble
  • Tighten all caliper mount bolts
  • Slowly push the brake pedal down and then up to take up air gap space between the brake pad and rotor
  • Bleed brake system as needed (note: if the system was never opened it probably does not need to be bled)
  • Inspect brake caliper and hose connection for leaks, if brake fluid leaks exist repair as needed and bleed system
  • Reinstall wheel and lug nuts, lower the tire onto the ground and then finish tightening lug nuts
  • NEVER MOVE A CAR WITHOUT NORMAL BRAKE PEDAL OPERATION
Visit - How to Replace Front Brake Pads and Rotors

Common Problems

  • When replacing a brake caliper make sure the sealing washer is not leaking
  • If a brake caliper slide has seized use an anti-rust solvent such as wd40 or equivalent
Preferred Procedure: When tightening any brake component including the lug nuts it should be done using a torque wrench to manufactures specifications.

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AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-01-06)