A flywheel is used primarily in manual transmissions. It is attached to the engine crankshaft and holds the ring-gear that is used to crank the engine. The wheel connects directly to the clutch, stores energy to move the vehicle from inertia, and provides a friction surface for the clutch to attach to. Because of this, these parts are usually cast, and are thick and heavy, to allow for the clutch’s surface. In addition, the heavy weight allows for more inertia once it is spinning.

Flywheels are usually produced by the casting method, and for now, sand casting is the most common production process for flywheels. Once cast, the flywheel is finished by machining and boring.