Everything You Need to Know About BrakesMar 15th, 2017
Brakes are a crucial component of any vehicle. Their purpose is to stop the vehicle by turning the motion of the rotating wheels into friction and heat. This action and conversion of energy is what stops the vehicle.
Types of Brakes
There are two types of brakes; Drum & Disc. Drum brakes get their name because of the drum shaped cover onto which the brake shoes apply a force to stop the vehicle. Drum brakes were the first type of brakes to be introduced for automotive applications. Early versions of drum brakes were actuated by a physical cable from the brake pedal to the drum itself.
However, once rubber seals were invented, the brake disc was also invented. When you apply pressure on the brake pedal, brake fluid flows to the brake caliper which clamps down on a brake disc thus turning motion into friction. Brake discs are relatively simpler in operation than brake drums and are more efficient at dissipating heat therefore they quickly became more popular than drum brakes.
Types of Discs
Brake discs are not quite as simple as most would think. Majority of vehicles are equipped with steel, one piece brake discs. These are inexpensive to manufacture and provide enough braking force for most situations. However in racing situations, one piece steel brake discs are usually not enough. This is due to the fact that the brake disc goes though a lot of heat cycles where the disc expands and contracts. This expansion requires space to occur but because the disc is made up of one piece, it cannot expand as much as it needs to so it warps. This warpage causes the brake pads to push back on the piston inside the caliper and in turn pushes back on the brake pedal though the fluid connection. This is why once a disc is warped you have to apply more brake pressure to compensate for the extra amount of space between the brake pad and disc. This is also what causes the brake pedal pulsation that you may feel when applying the brakes.
To get around this problem, some auto manufacturers utilize two-piece rotors made out of steel with an aluminum central “hat” or carbon ceramic with an aluminum central “hat”. The “hat” is the piece in a two-piece rotor that connects the wheel hub to the brake disc. This two-piece design allows for the steel or carbon ceramic disc to expand under high heat situations without warping. Normally these types of brake discs are used only on high performance vehicles such as the Chevrolet Corvette and are more expensive to manufacture.
Calipers are the solid stationary pieces that clamp down onto the rake disc to stop it from turning. This is achieved by fluid entering the caliper which pushes onto one or multiple pistons inside the caliper which in turn pushes on brake pads that make contact with the brake disc. A floating caliper is the most common type of caliper and is used on almost every vehicle on the road today. These are inexpensive to manufacture and they allow for some brake disc warpage before it is felt through the brake pedal. Fixed calipers are the second type and these are usually found on high performance cars and more recently on trucks. The main advantage of these types of calipers is that they allow for a bigger brake pad with more surface area. However the drawbacks of these calipers are that they cost more to manufacture and are more prone to transmit the feeling of warpage to the brake pedal.
Types of Brake Pads
Like most other brake components, there are two types of brake pads as well. Adherent and abrasive pads are what auto manufacturers primarily choose to use on their vehicles. Adherent pads are worn down or “eaten away” by the brake disc. They are usually less expensive than abrasive pads and produce less noise and dust. Abrasive pads are made up of materials that tend to wear down or “eat away” at the brake disc. These types of pads are generally found on many European and performance vehicles where quick stopping performance is required. They are more prone to noise and dust and also require a brake disc replacement when the vehicle is getting a brake service.
Types of Brake Fluids
There are 4 types of brake fluids to choose from and are categorized as DOT 3, DOT 4, DOT 5, and DOT 5.1. Brake fluid is a hydraulic fluid that is made up of primarily Glycol Ether or Silicone in the case of DOT 5 fluid. The different ratings refer to the temperatures they can endure before they reach their boiling points. DOT 3 has the lowest boiling point at just 205℃ whereas DOT 5 and DOT 5.1 can withstand temperatures up to 260℃. Majority of vehicles use DOT 4 while performance vehicles use DOT 5.1. DOT 5 fluid is much more uncommon than the others and this is because it cannot be mixed with any of the other fluids. However it does have the advantage that it is considered a hydrophobic liquid, that is, it does not absorb water which can significantly lower the boiling point.
Unfortunately to most, brakes are often overlooked when it comes to proper maintenance. They are considered by many as the most important components of a vehicle because they are a safety feature.