What Is a Brake Pad?
Brake pads are one of the components of brake calipers in disc brakes, and together with disc rotors, they are one of the most important components that directly affect the braking action of a car or motorcycle.
Brake pads are installed so that the disc rotor is sandwiched between the brake pads from the inside and outside. By sandwiching the disc rotor, which rotates together with the wheels of the car or motorcycle, the brake pads generate frictional heat to stop the rotation of the wheels.
Since these parts generate friction directly with the disc rotor, brake pads gradually wear out with use. As they wear out, braking power decreases, so they are also a component that needs to be replaced periodically.
Uses of Brake Pads
Brake pads are components directly related to the operation of disc brakes. Therefore, they are installed in automobiles and motorcycles equipped with disc brakes, or in railroads, aircraft, construction machinery, and agricultural machinery that uses disc brakes.
In recent years, along with the spread of EBS (electronically controlled brake systems), disc brakes are now being used in commercial vehicles, where drum brakes were the norm.
Principle of Brake Pads
Although the method of brake actuation differs from that of a car, in which the brake pedal is depressed, to that of a motorcycle, in which the brake lever is pulled, the method and principle of brake actuation are the same.
By depressing the brake pedal in the driver’s seat of a car or pulling the brake lever of a motorcycle, this force is amplified by a doubling device called a brake booster.
This force is then converted to hydraulic pressure at the master cylinder, which applies pressure to the pistons in the Brake Calipers. The pressure pushes the piston against the disc rotor, causing friction between the Brake Pads and the disc rotor.
The energy of the rotational motion is released outward as thermal energy generated by the friction, and this is how the wheel stops rotating. Therefore, a brake can be said to be a device that mechanically converts kinetic energy into heat and reduces the kinetic energy of the wheel.
Types of Brake Pads
Brake pads can be broadly classified into the following four categories according to the materials used.
- Non-asbestos materials
- Semi-metallic materials
- Carbon metallic material
- Metallic materials
“Non-asbestos materials” are widely used in general, and each type has its own merits and demerits.
1. Non-Asbestos Material
This material is most commonly used in brake pads for Japanese automobiles and motorcycles because it causes less brake noise (squeal), brake dust, and load on the disc rotors.
Although its heat resistance is not very high, it is said to be the most suitable material for driving in urban areas. If you are not particularly particular about driving performance, non-asbestos material Brake Pads are the best choice.
2. Semi-Metallic Material
Semi-metallic brake pads have excellent controllability and wear resistance, and provide stable braking performance even when driving on circuits or in other conditions where the brakes are subjected to heavy loads. On the other hand, it has disadvantages, such as a tendency to generate brake noise (squeal) and to stain wheel wheels.
Semi-metallic material is recommended if you want to use one brake not only for city driving but also for circuit driving.
3. Metallic Material
This material is mainly used as brake pads for vehicles that are driven on circuits, such as racing cars. It has excellent heat resistance performance, and it provides outstanding braking and control performance even at high speeds and under high brake loads such as in circuit driving.
However, it is also prone to brake noise (squeal) and wheel contamination, and is difficult to brake at low speeds, placing a high load on the disc wheel.
Another disadvantage is that they deteriorate more quickly than non-asbestos or semi-metallic materials and must be replaced more frequently. It is not suitable for city driving and is best suited only for circuit driving.
4. Carbon Metallic Material
This material has excellent heat resistance and braking performance, and like metallic materials, it is also used in racing cars that are driven on circuits. It is prone to brake noise (squeal) and wheel contamination, and places a heavy load on the disc rotor.
However, it can also be used for city driving, as braking does not deteriorate at low speeds, as with metallic materials. They are best suited for sports cars and other vehicles where you want to enjoy a stable driving feel.
Other Information on Brake Pads
Brake Pads Life Span and Replacement Timing
Brake pads are used as friction materials, so they will wear out and braking performance will deteriorate over a long period.
Therefore, it is necessary to periodically replace brake pads at one’s own discretion when the brake pads have decreased to 3 mm or less, or when the vehicle has traveled 30,000 to 50,000 km in terms of mileage.
In addition, regardless of the decrease in brake pads or the mileage, if the brakes become less effective or if abnormal noises are heard when braking, it is likely that there is something wrong with the operation of the brake pads. Since these parts are directly related to vehicle safety, it is important to inspect and replace them as soon as possible in case of an emergency.