The Modern Disk Brakes

The disk brake is the best brake we have found so far.

Disk brakes are used to stop everything from cars to

locomotives and jumbo jets.  Disk brakes wear longer,

are less affected by water, are self adjusting, self cleaning,

less prone to grabbing or pulling and stop better than any

other system around. The main components of a disk brake

are the Brake Pads, Rotor, Caliper and Caliper Support. 

Brake Pads 

There are two brake pads on each caliper. They are constructed

of a metal "shoe" with the lining riveted or bonded to it.   The pads

are mounted in the caliper, one on each side of the rotor.  Brake

linings used to be made primarily of asbestos because of its heat

absorbing properties and quiet operation; however, due to health

risks, asbestos has been outlawed, so new materials are now

being used.  Brake pads wear out with use and must be replaced

periodically. There are many types and qualities of pads available.

The differences have to do with brake life (how long the new pads

will last) and noise (how quiet they are when you step on the brake).

Harder linings tend to last longer and stop better under heavy use

but they may produce an irritating squeal when they are applied.

Technicians that work on brakes usually have a favorite pad that

gives a good compromise that their customers can live with.

Brake pads should be checked for wear periodically. If the lining

wears down to the metal brake shoe, then you will have a "Metal-to-Metal"

condition where the shoe rubs directly against the rotor causing severe

damage and loss of braking efficiency. Some brake pads come with a

"brake warning sensor" that will emit a squealing noise when the pads

are worn to a point where they should be changed.  This noise will usually

be heard when your foot is off the brake and disappear when you step

 on the brake.  If you hear this noise, have your brakes checked as soon

as possible.


The disk rotor is made of iron with highly machined surfaces where the brake pads contact it.  Just as the brake pads wear out over time, the rotor also undergoes some wear, usually in the form of ridges and groves where the brake pad rubs against it.  This wear pattern exactly matches the wear pattern of the pads as they seat themselves to the rotor.  When the pads are replaced, the rotor must be machined smooth to allow the new pads to have an even contact surface to work with.  Only a small amount of material can be machined off of a rotor before it becomes unusable and must be replaced.  A minimum thickness measurement is stamped on every rotor and the technician doing the brake job will measure the rotor before and after machining it to make sure it doesn't go below the legal minimum.  If a rotor is cut below the minimum, it will not be able  to handle the high heat that brakes normally generate.  This will cause the brakes to "fade," greatly reducing their effectiveness to a point where you may not be able to stop!  One of the major purchases a consumer will make is that of an automobile. After investing that much money in a product, it only stands to reason that the purchaser would want to keep the vehicle in optimum working order to maintain proper function and safety. One system that is often overlooked until serious issues arise is the braking system, and more specifically, the rotors in the braking system.

The Function of a Rotor

A rotor is a part of a vehicle’s braking system. It is roughly shaped like a flat-bottomed bowl with a wide lip at the top. The calipers and pads of the brake press against the sides of the rotor when the brake is applied, causing friction to stop the vehicle. The design of the rotor allows the heat produced by this process to be evenly dispersed throughout the braking system so it does not overheat. Normal use of the brakes will eventually wear the various parts of the brake system, and if they are not checked and replaced regularly, damage can occur. If this damage is not addressed, it can progress to the point that the brakes are ineffective and might totally fail, putting the vehicle and its occupants in danger. The good news is there are easy ways to tell if a rotor is bad so the owner may seek services to correct the problem.

How to Tell if a Rotor is Bad

Through everyday use, parts in the brake system wear, particularly the brake pads. When the brake is applied, calipers push the pad against the wall of the rotor causing friction, which slows the car and allows it to stop smoothly. Because of this friction, the brake pads begin to wear down. If the brake pad ever wears below a quarter of an inch, it needs to be replaced. The best way to know if the pad is wearing too much is to look at the brake pad through the space on the wheel. Another way is through the high-pitched sound the brake will make when it is applied. There is a small metal shim called an indicator that will create this sound every time the brake is applied if the pad has worn down too far.

Putting New Pads on a Bad Rotor

There are times when a car owner knows the rotors are bad and need to be replaced but finances are tight. They may try to replace the more inexpensive brake pads, hoping this will address the problem for a while. In actuality, it is just as bad or worse.

The brake pad relies on friction as it is pressed against the rotor to help stop the car. If a new brake pad is put onto a vehicle with damaged rotors, the pad will only contact the highest points on the surface, which will reduce its stopping ability. Deep grooves that have been cut into the rotor will act much like a cheese grater and shred the pad material as it is pressed against the rotor.

Another side effect will be an increase in the heat caused by the malfunctioning parts. Since the rotor is no longer able to evenly distribute the heat generated by the braking process, hotspots will occur, indicated by a blue color on the rotor. If evidence of this overheating is found on the rotors, there is no alternative but to replace the rotors.


Two Brothers Auto Service

     561-712-1100    1655 Donna Road - Bay 45, West Palm Beach FL 33409


Aboe is a sign of warped rotors that have an uneven surface. The rotor will cause a pulsating vibration when brakes are applied due to the uneven surface. The rotors must be replaced.


These should be replaced

Above is a sign of cracked rotors. This is caused by high heat which has caused cracks in the rotor usually as a result of rotors being too thin. New pads will squeel, lose stopping power and wear prematurely.

Above is a sign of a glazed rotor. This is caused by extensive wear which creates slick, shiny metal. New pads will lose stopping power as there is insufficient grab from the rotor to the brake pad.

Above are grooved rotors that have been damaged. New brake pads without replacing the rotors will cause premature wear and lack of stopping power