Jarrulevyn

Jarrulevyn is the Finnish term for the brake disc, a rotating component in a vehicle’s disc braking system. It is mounted to the wheel hub and provides a friction surface against which the brake pads press to slow or stop the wheel, converting kinetic energy into heat.

Most jarrulevyt are made of cast iron, though steel and composite materials are used in specialized applications. Common designs include solid rotors and ventilated rotors, which have an internal air gap to improve cooling. Some rotors are finished with cross-drilled holes or slots to aid heat dissipation and reduce pad glazing, though such features can increase wear and are not suitable for all driving conditions.

During operation the rotor experiences high temperatures and thermal cycling. Heat can cause warping or brake fade if cooling is insufficient. Rotor thickness wears with use; manufacturers specify a minimum thickness, at which point the rotor should be replaced. Resurfacing can restore a true surface but reduces thickness.

Maintenance involves visual inspection for cracks, scoring, and corrosion, as well as measurement of rotor thickness and runout. Rotors are typically replaced with new brake pads, and the assembly should be torqued according to manufacturer specifications. Proper matching of rotor and pad materials is important for braking performance and rotor longevity.