Replacing Brake Pads

by Admin on August 8, 2011

sReplacing Brake PadsBrake pads are the friction material that press against the rotor to stop a vehicle when the brake pedal is depressed.  The brake pad is comprised of brake a brake lining material fastened to a metal back.  Linings are either bonded, riveted or even integrally molded to the metal backing.  Linings can either be asbestos, semi-metalic and even ceramic.  Some brake pads have wear sensors, which are small metal tabs that rub against the rotor  when the lining gets thin, creating noise that alerts the driver to get the brakes inspected.

Brake System Fundamentals

Liquid under pressure can be used to transfer motion or multiply and apply force.  This is called hydraulics.  When the brake pedal is depressed, it moves a piston in the master cylinder.  This piston forces fluid through brake lines and hoses to hydraulic cylinders at each wheel.  The hydraulic cylinders used on the front wheels are brake calipers and usually wheel cylinders at the rear wheels although many car models nowadays use calipers on all four wheels.  Disk brakes are more expensive than Drum brakes but also perform better.  This is due to the disk brake’s ability to dissipate heat through the vented rotors.  By contrast the heat generated in drum brakes is contained inside the drum.

Brake Fluid

Most brake fluids are glycol-based and have DOT ratings based on its boiling point.  Some of the heat generated in the braking process is transferred to the brake fluid, making a high boiling point desirable.  Dry boiling point is defined as the boiling point of new fluid as opposed to wet boiling point, which would be the boiling point of brake fluid containing 2% moisture.  Brake fluid by its nature absorbs moisture from the air.  DOT 3 and DOT 4 are commonly used in the industry.   Synthetic silicone-based brake fluid was developed in the early 1970s and a new category was created, DOT 5.  DOT 5 brake fluid has a higher boiling point and is not hygroscopic (does not absorb moisture).  Synthetic brake fluids last longer than conventional brake fluids.

Brake pad life depends on many factors including driver habits and the overall condition of the brake system.  The brake pad wear patterns are a good diagnostic tool to determine the cause of brake problems.  Uneven wear is usually a sign of caliper hardware or slide problem.  Cracks on the friction material can indicate a overheating situation caused by a sticking caliper piston, collapsed brake hose or even the rotor thickness being below specifications.

The best way to diagnose brake problems is to look at the brake system as a whole instead of just replacing brake pads.  A proper diagnosis is essential to keeping your brake system functioning properly, keeping you and your family safe and minimizing costly repairs.  Brakes are available at any local auto parts store.

Leave a Comment

Previous post:

Next post: