Vehicle wheel and brake disc apparatus

A wheel and brake disc apparatus of a vehicle, comprising:

• a roadway wheel and a brake disc secured to a hub of an axle of the vehicle, the roadway wheel and the brake disc arranged about an axis of rotation of the hub;
• the roadway wheel extending radially in relation to the axis of rotation to a wheel rim configured to hold a tire adapted to operate on a roadway surface;
• the brake disc inboard of the roadway wheel and extending radially in relation to the axis of rotation to a disc rim from an open end of a hat extending outward from the brake disc to an assembly comprising an inwardly-directed flange secured to the hub, the hat defining a volume between the open end and the assembly, and the axle extending through the volume to the hub from the open end;
• a radial rotary bearing in the volume, the radial rotary bearing coupled between the axle and the hat and configured to support radial loads therebetween;
• a brake caliper assembly mounted at a fixed location over the brake disc rim and configured to squeeze brake pads against the brake disc;
• and
• the brake disc rim comprising a tread configured to operate on a rail without interference from the brake caliper assembly.