We all know that in today’s family cars, the braking systems typically come down to either disc brakes (also known as "dish brakes") or drum brakes. In the eyes of most people, disc brakes symbolize sophistication and high-end performance, while drum brakes are seen as outdated and inferior. But is this really the case? Let’s examine each system one by one.

I. Disc Brake

1. Components

Typically, the primary components of a disc brake system include: the master cylinder, wheel cylinders, brake discs, brake calipers, brake pads, brake lines, and more.

2. Braking Principle

The braking principle of disc brakes is simple yet remarkably straightforward: when the vehicle needs to slow down, the brake caliper clamps onto the brake rotor. This action creates friction between the brake pads and the rotor, gradually reducing the car's speed—much like how you can pinch a sheet of paper between two fingers. The brake caliper is pushed by a brake piston, and the piston’s movement is powered by hydraulic pressure. During braking, the vehicle’s original kinetic energy is converted into heat, which is then dissipated into the surrounding air.

3. Advantages

Because the brake disc in a disc brake system is exposed to the air, it benefits from direct air cooling during driving, allowing for relatively quick temperature reduction and preventing rapid brake fade. Additionally, the force with which the piston pushes the brake caliper to clamp down on the brake disc has a linear relationship with how hard the driver presses the brake pedal, giving the driver easier control over braking intensity.

4. Defects

Vehicles equipped with disc brakes always require a brake booster system, as the driver’s foot alone cannot generate sufficient braking force. In most vehicles, this brake booster relies on a vacuum brake booster pump, which typically draws its vacuum from the negative pressure created in the engine’s intake manifold. This explains why, after parking and turning off the engine, you often need only "one firm press" of the brake pedal—because by the time you press again, the vacuum assistance has already dissipated, leaving the pedal as hard as a rock.

II. Drum Brakes (Drum Brake System)

1. Some components

A typical drum brake is primarily composed of components such as the backing plate, brake drum, brake shoes, wheel cylinder (also known as the brake caliper), return springs, and locating pins.

2. Braking Principle

The brake drum is mounted directly onto the wheel hub and rotates along with the wheel. It’s made from cast iron of a specific weight, giving it a shape that resembles a cylindrical drum. When braking, the wheel cylinder piston pushes against the inside surface of the brake drum, creating friction that slows down the drum—and consequently, the wheel—ultimately bringing the vehicle to a stop.

Of course, the machining and construction of drum brake components are relatively simple, which significantly reduces manufacturing costs. That’s precisely why we believe drum brakes represent a factor of basic equipment and poor quality.

3. Drawbacks

Since it's essentially a nearly closed brake drum, the heat dissipation capability of drum brakes is significantly worse than that of disc brakes. After heating up, the diameter of the brake drum expands, which in turn increases the travel distance required when pressing the brake pedal—and this easily leads to brake fade due to overheating.

Due to the drum brake having another advantage—seemingly not a major one—compared to disc brakes: the return spring. Thanks to this spring, when braking is no longer needed (when the brake is released), the brake shoes instantly separate from the brake drum, preventing even the slightest waste of extra energy. In contrast, the separation between disc brake pads and rotors isn’t quite as swift. While this energy loss is minimal, for a compact, battery-powered electric vehicle, it can make a significant difference—enabling the car to travel farther on a single charge.