I claim the ornamental design for a disc brake rotor portion, as shown and described.
FIG. 1 is a perspective view of a first embodiment of a disc brake rotor portion showing my new design;
FIG. 2 is a front view of the disc brake rotor portion shown in FIG. 1, with the rear view being a mirror image;
FIG. 3 is a perspective view of a second embodiment of a disc brake rotor portion showing my new design; and,
FIG. 4 is a front view of the disc brake rotor portion shown in FIG. 3, with the rear view being a mirror image.
The portions of the disc brake portion shown in dot-dash lines define the boundary of the claimed design and form no part of the claimed design. The portions of the binder shown in dashed lines illustrate environment and form no part of the claimed design.