The ornamental design for a tire tread, as shown and described.
FIG. 1 is a perspective view of the tire tread, showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is an enlarged partial front elevation view thereof;
FIG. 4 is a right side elevation view thereof; and,
FIG. 5 is a left side elevation view thereof.
The tire tread pattern is repeated uniformly around the circumference of the tire. The dash-dot lines showing the boundaries of the claim and the broken lines depicting environmental structure (the sidewall of the tire) do not form a part of the claim.