The ornamental design for a tire tread, as shown and described.
FIG. 1 is a perspective view of a tire tread showing our new design, it being understood that the tread is repeated throughout the circumference of the tire, the opposite side perspective being identical thereto, it being understood that the sidewall forms no part of the claimed design;
FIG. 2 is a front elevation view thereof, the rear elevation view being identical thereto;
FIG. 3 is a side elevation view thereof, the opposite side elevation view being identical thereto; and,
FIG. 4 is an enlarged view of a portion of the tire tread of FIG. 2.