This brake disc is the rotating friction surface in the tractor's service brake system. It is splined to the axle shaft and is clamped between stationary friction pads when the brake pedal is applied. The disc converts kinetic energy into heat through friction, slowing or stopping the wheel hub. A worn disc reduces braking force and can cause uneven pad wear or brake chatter. The disc is manufactured to the original spline geometry and thickness specification, which ensures proper engagement with the hub and consistent clamping force from the caliper assembly. When replacing, inspect the mating hub splines for wear and install new friction pads against the fresh disc surface.