The rotor (or disc) is a cast iron component in a disc brake system. The main function of the rotor is to dissipate the heat that is generated during braking events. The rotor dissipates the heat via conduction, convection, and radiation. The thermal storage capacity of the rotor is important to allow the rotor to store the stopping energy before it can fully dissipate it. Front rotors absorb up to 80% of the heat, so they usually are vented with ribs, while rear rotors absorb less and are typically solid discs. A brake drum operates in a similar manner like a rotor, but is designed to work with a brake drum assembly instead of a caliper.