The brakes are one of the most important safety features of any vehicle, but this system is easily neglected and taken for granted until a problem arises. Improper care of the brake system is not only a safety risk, but may lead to brake component replacement and repairs, including grooved or warped brake rotors and worn out brake pads. It may also cause the brake system to overheat, which could result in a loss of braking power. There are two types of brake systems: disc brakes and drum brakes. Most modern vehicles have disc brakes. However, some models still use front disc brakes and rear drum brakes. Disc brakes use brake calipers to squeeze the brake pads against the brake rotors when the brake pedal is depressed. Drum brakes use a wheel cylinder to push the brake shoe out against the inside of the drum to stop the vehicle. These components are powered by the master cylinder, which pressurizes the brake fluid that runs throughout the braking system. To maintain the brakes on a vehicle it is necessary to make sure the brake fluid is clean and topped-off, change the brake pads or brake shoes when needed, and keep the brake calipers and brake hardware clean and free from corrosion. Since drum brakes are mostly enclosed, they are less prone to coming into contact with debris, but still should be checked periodically. A good time to inspect the drum brakes is during a tire rotation.