2-Piece Brake Rotors

A two-piece brake disc separates the friction ring from the centre section. The ring is cast iron; the centre, or hat, is usually aluminium, and the two are joined by bobbins or drive pins. In a floating design the ring can move slightly on those fixings as it heats and expands, which reduces stress in the ring. Fixed designs bolt the two rigidly together. With an aluminium hat, a two-piece disc is usually lighter than a one-piece disc of the same size.

Two-piece discs here are listed either as complete assemblies, ring and hat together, or as replacement rings for an existing hat. When a ring wears out, only the ring needs replacing. Most have curved internal vanes and a curved-slot face. Curved vanes are directional, which is why these discs are sold as left or right parts rather than as an axle pair. Some listings give the diameter and thickness, and a few note a wide annulus for pads with a deeper friction area.

Order the correct side for each corner, and check that the disc diameter and thickness match your calipers and the inside of your wheels.

When fitting a ring to a hat, use new bolts or drive hardware where the maker specifies, torque them in sequence, and use thread-locking compound if instructed. Inspect the bobbins or pins for wear at each pad change, and bed in new pads on a new ring before driving hard.