Jarrulevyt

Jarrulevyt are a key component of disc brake systems used in most modern road vehicles. In Finnish, the term jarrulevyt refers to these brake discs. They are the rotating discs to which brake pads grip when the brake is applied, converting kinetic energy into heat that slows and stops the vehicle. The disc is mounted to the wheel hub and rotates with the wheel; the caliper remains stationary and clamps the pads onto the disc.

Discs come in several forms. The most common are solid discs and ventilated discs, the latter featuring internal vanes to improve cooling. Performance-oriented setups may include drilled or slotted discs to aid heat dissipation and pad bite, but drilling can increase the risk of cracking and may affect strength and longevity.

Jarrulevyt are typically made from cast iron, which provides a balance of strength, heat capacity and cost. Some light and high-performance applications use aluminum or composite materials, and carbon-ceramic discs are employed in premium vehicles for reduced weight and enhanced high-temperature performance. The choice affects braking feel, noise, wear and cost.

Over time, discs wear as pads abrade their surface. Inspection is needed for scoring, grooves, cracks, rust, and runout. If the disc is worn below its minimum thickness or shows excessive runout, it should be machined (resurfaced) or replaced. Replacement is usually paired with new pads, and both parts should meet manufacturer specifications.