Definition: A round mechanical unit used as part of a braking system. The rotating disc is gripped by two (or more) brake pads to slow a motorcycle. These items are known as rotors in the United States.

Alternate Spellings: Rotors

Examples: Early disc brake systems were notorious for their poor performance in wet conditions. As new materials were developed, namely sintered pads, the braking efficiency improved considerably.

However, improved pad materials initially resulted in high wear rates of the discs.