Drum brakes and disc brakes are two common types of braking systems used in vehicles, each with its own advantages and disadvantages. Here are the key differences between drum brakes and disc brakes: 

Operating Principle: 

Drum Brakes: Drum brakes operate on the principle of friction created by brake shoes pressing against the inner surface of a rotating brake drum. When hydraulic pressure is applied, the brake shoes expand inside the drum to create friction and slow down the vehicle.

Disc Brakes: Disc brakes operate by clamping brake pads onto a rotating brake disc (also known as a rotor). The friction generated between the brake pads and the disc is what slows down the vehicle. 

Heat Dissipation: 

Drum Brakes: Drum brakes are less effective at dissipating heat compared to disc brakes. Heat buildup can occur during heavy braking, potentially leading to reduced braking performance (brake fade).

Disc Brakes: Disc brakes are better at dissipating heat due to their open design, which helps prevent brake fade and maintains consistent braking performance, especially during repeated or heavy braking. 

Braking Performance: 

Drum Brakes: Drum brakes are generally less effective in providing rapid and powerful stopping, particularly in high-performance or heavy-duty applications. They are more commonly found on rear wheels in modern vehicles.

Disc Brakes: Disc brakes offer superior stopping power and responsiveness, making them the preferred choice for the front wheels of most vehicles. They are capable of providing better performance under various driving conditions. 

Maintenance and Serviceability: 

Drum Brakes: Drum brakes are typically more complex and harder to service compared to disc brakes. They require more labor and time for inspection and replacement of brake shoes and other components.

Disc Brakes: Disc brakes are easier to inspect and service since the brake pads and rotors are readily accessible. This results in quicker and often more cost-effective maintenance. 

Weight and Size: 

Drum Brakes: Drum brake systems are generally more compact and lighter than disc brake systems. This can be advantageous in some applications where space and weight considerations are important, such as in the rear wheels of smaller vehicles.

Disc Brakes: Disc brake systems are larger and heavier but offer better performance. They are typically used on the front wheels of most vehicles to handle the majority of braking work. 

Cost: 

Drum Brakes: Drum brake systems are generally less expensive to manufacture and install, which can make them an attractive option for cost-sensitive applications.

Disc Brakes: Disc brake systems are typically more expensive to manufacture and install, but they offer better performance, which is often considered worth the added cost. 

In summary, while both drum brakes and disc brakes have their own advantages and disadvantages, disc brakes are generally favored for their superior braking performance, heat dissipation, and ease of maintenance. However, drum brakes are still used in certain vehicle configurations and applications where cost or space considerations are more important than high-performance braking.