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, it being understood that the pattern is repeated uniformly throughout the circumference of the tread;
FIG. 2 is a front elevational view thereof, the rear elevational view thereof, and the top and bottom plan views thereof are the same;
FIG. 3 is a left and right side view thereof, the views being the same; and,
FIG. 4 is an enlarged fragmentary view taken from FIG. 2.
The broken line defining the sidewall, inner bead and the peripheral boundary between the tire tread and sidewall are for the purpose of illustrating environment and form no part of the claimed design.