A Comprehensive Guide to Brake Pads: Practical Knowledge from Principles to Maintenance
As the core component of a car's braking system, brake pads are directly related to driving safety but are often overlooked by most car owners. Many people only realize there is a problem when abnormal noises occur during braking or the braking distance becomes longer-and by then, potential safety hazards usually already exist. This article will comprehensively sort out key knowledge about brake pads, covering their basic composition, type differences, working principles, replacement cycle, purchasing skills, and daily maintenance, to help car owners establish a scientific maintenance awareness.
I. Core Composition of Brake Pads: More Than Just "a Piece of Iron"
Brake pads are not a single structure but a precise combination of multiple functional layers. Each layer performs its own role to jointly achieve stable braking. Their typical structure includes four layers:
1. Friction Layer
As the outer layer in direct contact with the brake disc, it is made of friction materials and serves as the key to generating braking force. A high-quality friction layer must meet three core requirements simultaneously: a high friction coefficient (to ensure braking effectiveness), a low wear rate (to extend service life), and low noise (to enhance driving experience). Common materials include resin, metal powder, and ceramic particles.
2. Heat Insulation Layer
Located between the friction layer and the backplate, its main function is to block the high temperature (up to 600-800℃) generated during braking from being transmitted to the brake caliper and wheel hub bearing-preventing metal components from deformation or failure due to overheating. It is usually made of high-temperature-resistant heat insulation glue or asbestos substitutes (asbestos has been banned in modern brake pads).
3. Adhesive Layer
It is responsible for firmly bonding the friction layer to the heat insulation layer, and the heat insulation layer to the backplate. Since it needs to withstand high temperatures and high-frequency vibrations, high-strength, high-temperature-resistant adhesives are used. Its bonding strength directly determines whether the brake pad will suffer from "chunking" failures.
4. Backplate
As the supporting structure of the brake pad, it is usually made by stamping steel plates, with anti-rust treatment (such as galvanizing or painting) applied to its surface. The backplate not only fixes the position of the brake pad in the caliper but also needs to be precisely matched with the caliper through the positioning holes and installation buckles on it-ensuring no deviation during braking.
In addition, some high-end brake pads are equipped with wear warning plates (thin metal sheets) or electronic sensors on the edge of the backplate: when the friction layer is worn down to the safety threshold, the warning plate will rub against the brake disc to produce a "squeaking" noise, while the electronic sensor will trigger the fault light on the instrument panel-reminding the car owner to replace the brake pads in a timely manner.
II. Differences Between Brake Pad Types: Metal, Ceramic, Organic-How to Choose?
Brake pads on the market are mainly divided into three types. Their material properties determine their applicable scenarios and user experience, so car owners should choose based on their vehicle model, driving habits, and usage environment:
1. Metal Brake Pads (Semi-Metal / Full-Metal)
Material Composition: Mainly made of metal particles (such as steel fibers, copper fibers, and iron powder) mixed with resin adhesives. The metal content is usually 30%-70%.
Core Features: It has a high friction coefficient (about 0.4-0.5 in dry conditions), strong high-temperature resistance (can withstand temperatures above 800℃), and stable braking performance. It is particularly suitable for scenarios involving high-speed driving or frequent braking (e.g., taxis and trucks).
Disadvantages & Precautions: It has high hardness, which causes relatively significant wear to the brake disc-long-term use may lead to scratches on the brake disc. Braking noise is more noticeable at low temperatures (below -10℃), and metal particles are prone to rust, so it is necessary to regularly check whether the edge of the brake pad is rusted.
Suitable for: Car owners who frequently drive on highways or mountain roads, or those who drive SUVs and heavy-duty vehicles.
2. Ceramic Brake Pads
Material Composition: Its core is inorganic non-metallic materials (such as ceramic fibers, aluminum oxide, and silicon dioxide), paired with a small amount of metal powder (e.g., copper powder for heat conduction). The metal content is usually less than 10%.
Core Features: It has a stable friction coefficient (small difference between dry and wet conditions, about 0.38-0.45), a low wear rate (service life is 30%-50% longer than that of metal brake pads), and causes little damage to the brake disc. There is almost no noise during braking, and no metal dust is generated (the wheel hub is less likely to turn black, reducing cleaning frequency). It also has excellent high-temperature resistance and anti-aging performance, making it suitable for long-term parking or use in high-temperature areas.
Disadvantages & Precautions: Its braking response is slightly slow at low temperatures (1-2 brake applications are required after a cold start to achieve optimal performance), and its price is relatively high (usually 1.5-2 times that of metal brake pads). It is not suitable for frequent heavy loads or extreme off-road scenarios.
Suitable for: Owners of family cars, those with high requirements for quietness and wheel hub cleanliness, or users who drive on urban roads for a long time.
3. Organic Brake Pads (Resin-Type)
Material Composition: Mainly made of organic materials (such as resin, rubber, and graphite), with no or very little metal particles.
Core Features: It has a soft texture, causing minimal wear to the brake disc, extremely low braking noise, and a low price (about half that of metal brake pads). It is suitable for low-speed, light-load braking scenarios.
Disadvantages & Precautions: It has a low friction coefficient (about 0.3-0.35) and poor high-temperature resistance (prone to thermal fading when the temperature exceeds 300℃, leading to brake failure). It also wears quickly (service life is usually only 20,000-30,000 kilometers) and is not suitable for high-speed or heavy-duty vehicles.
Suitable for: Owners of low-speed electric vehicles, elderly scooters, or micro-cars that only travel short distances in urban areas.
