The ornamental design for a tire tread, as shown and described.
FIG. 1 is a side perspective view of a tire tread showing my new design, it being understood that the tread pattern is repeated throughout the circumference of the tire tread, the opposite side being the same as that shown;
FIG. 2 is a front elevation view thereof, the opposite side being identical thereto; and,
FIG. 3 is a side elevation view of the right side thereof, the left side elevation being identical thereto.
The broken line showing of a tire sidewall and inner bead depicts environment and forms no part of the claim.