The ornamental design for a tire tread, as shown and described.
FIG. 1 is a perspective view of a portion of a tire tread of our new design, the back view, the top view and the bottom view are all same images of the front view; and,
FIG. 2 is a front view thereof.
The broken line showings of the remainder of the tire are for illustrative purposes only and form no part of the claimed invention.