Measuring brake wear

A final drive assembly is driven by an electric motor and includes a park and service brake arrangement including a shared disc brake pack that is compressed by a preload exerted by a compression spring arrangement defined by a stack of Belleville springs for establishing an engaged park brake condition in the absence of pressurized brake actuating fluid being routed to a park brake piston. An electrical control is provided for computing disc brake pack wear based on a stored load curve of the stack of Belleville springs containing information correlating preload amounts to various compressed heights of the stack of Belleville springs, and on the magnitude of a drive signal sent to the electric motor for causing sufficient drive torque to be developed for causing the rotor discs of the engaged disc brake pack to slip relative to the stator discs.