What must be replaced occasionally in a drum brake system?

In a drum brake system, the components that require occasional replacement are the shoes and the drums. Brake shoes are the friction components that press against the inside of the drum to create the necessary stopping power when the brakes are engaged. Over time and with usage, these shoes wear down due to constant friction.

The drums, while more durable than the shoes, can also be subject to wear, warping, or scoring, which necessitates their replacement to ensure safe and effective braking performance. When either component becomes worn or damaged, it can significantly affect the braking efficiency and safety of the vehicle.

The other components mentioned, such as calipers and rotors, are associated with disc brake systems rather than drum brakes, and while brake fluid and lines do require periodic maintenance, they do not typically need replacement as frequently as the shoes and drums in a drum brake system.