Article describes how automotive brake pads work.
Brake pads are designed to absorb heat as they create friction against the brake
rotor when the brake pedal is activated. These pads ride against either side of
the rotor which are held in place by the brake caliper which is typically mounted
to the spindle or backing plate. Hydraulic pressure is provided by the brake system
via a brake master cylinder. When the brake system is activated the brake pads are
forced against the brake rotor causing it to slow down, in turn slowing the motion
of the car. Heat is created and dissipated through the pads and rotors. If a brake
pad or rotor becomes overheated it can hinder the brake operation until cooled because
no additional heat can be absorbed which is known as brake fade.
Brake pads are designed to withstand the amount of pressure provided by the master
cylinder. While the backing plates of all brake pads are made of metal there are
several different classifications of the brake composite, for example; organic,
semi metallic and ceramic to name a few. The organic pad is used mainly for stock
applications, the semi metallic is used for trucks and SUV's while the ceramic pad
is used for extended life applications. Each of these pads possess individual wear
and usage characteristics, for example; organic pads are the most forgiving pad
when it comes to brake rotor wear, and tend to make less brake noise such as squeaking.
Semi metallic pads tend to be more abusive to the rotors but can take more heat
then organic pads before brake fade occurs. Ceramic pads are the hardest pad of
the group and can wear out the rotors over the life of the brake pad. Ceramic pads
can also be associated with brake pad producing noises like squeaking, grumbling
and other undesirable characteristics. The advantage of the ceramic pads is the
lifespan of the brake pad set is about 20% longer than a regular brake pad. Every
brake pad manufacturer has their own mixture of composite material that can vary
in cost and quality. This material is bonded or riveted to the metal backing plate
that is fitted into the brake caliper.
Front Brake Pads (appearance will vary)
When servicing or replacing brake pads it is advised to wear a breathing mask
over your nose and mouth to avoid inhaling brake dust particles. It is also advisable
to wear gloves to avoid skin irritation. These dust particles have been known to
cause health problems when exposed to them for an extended amount of time. When
replacing brake pad always match the old brake pads to the new brake pads. The backing
plate of the brake pad should be identical to the old brake pads, except for the
missing brake pad composite material. Some brake pads are fitted with anti rattle
clips. These clips are design to allow the brake pads to move freely within the
If these clips are not included with the brake pad set transfer the old clips
to the new brake pads set. Do not discard the anti rattle clips this will result
in the brake pad having excessive clearance which will create a pop or click sound
when the brakes are applied. Some brake pad design will include a screamer style
of wear indicator. This minimum thickness indicator was created to make a "chirping
or screaming noise" when the brakes are in the "idle" position or when the brakes
are applied. In an effort to help keep the brake pad in place manufacturers have
designed "built in" clips that hold the pad to the inside and outside of the caliper.
The inboard pad clip fits inside the caliper piston while the outboard pad clip
attaches to the outer part of the caliper. These clips hold the brake pads into
the brake caliper.
Squeaking or Grumbling Brakes
Brake squeak is one of the most common problems that can occur when the brakes
are in operation. The brake squeaking noise is caused by ultra small vibrations
that develop into an audible frequency. There are a number of reasons brakes can
produce this noise. The most common cause of brake squeak is cheap or inferior brake
pads and rotors which are made using sub-par material and below average manufacturing
These brake components tend to wear out more rapidly with below average performance
characteristics. There is additional steps you can take to help insure quiet brake
operation. When installing new brake pads use brake pad shims. These shims act as
a shock absorber to dampen brake vibration which will help stop brake squeak. Heat
can affect brake pads in a negative way, if the brake pad has been over heated it can
cause the composite material to become crystallized, when crystallization occurs
the brake pad becomes harder.
If a brake pad is hardened it can cause brake squeak. Once the condition has
occurred replacement is required. When replacing brake pads a brake rotor replacement
or re-machine is needed.
When a brake pad is used it will develop an un-even surface across the face of the
brake rotor. If new brake pads are installed onto a worn brake rotor it can cause
weak brake operation and squeaking. This can cause the brake pedal or steering wheel
to pulse when the brakes are in operation.
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Brake pad replacement
Article first published 2016-02-03