Offset?
I doubt, however, that this definition of offset applies to one-piece rotors. In this case, offset is <i>probably</i> the distance from the hat's hub mounting surface to the centerline of the rotor (add 1/2 of the rotor width to the above hat offset).
For a radial mount caliper, the similar dimension that counts is the distance from the centerline of the caliper's mounting bolts to the centerline of the rotor, 42 mm in this pdf of my <a href="http://www.hrpworld.com/client_images/ecommerce/client_39/products/pdf_1015_1.pdf">Alcon TA6</a>.




