The ornamental design for a tire tread, as shown and described.
FIG. 1 is a perspective view of a tire tread showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is an enlarged front view of a portion thereof; and,
FIG. 6 is an end view taken along line 6-6 in FIG. 5.
Broken lines in the drawings are intended to show portions of the tire that are not being claimed, and thus form no part of the claimed invention. The dashed line represents a border between claimed and unclaimed subject matter.