jarrupyörä
A jarrupyörä, often translated as brake disc or rotor, is a component of a disc brake system. It is a circular metal plate that rotates with the wheel of a vehicle. When the brakes are applied, brake pads clamp onto the surfaces of the jarrupyörä, creating friction. This friction converts the kinetic energy of the vehicle into heat, which slows down and eventually stops the vehicle.
Jarrupyörät are typically made from cast iron, steel, or sometimes more exotic materials like carbon-ceramic composites
The design of a jarrupyörä can vary. Solid discs are simpler and used in many lighter vehicles.