The ornamental design for a tire tread, as shown and described.
FIG. 1 is a front left perspective view of a tire tread showing our new design, the design repeated about the circumference of the tire tread, it being understood that the dashed lines form no part of the claimed design;
FIG. 2 is a front elevation view thereof, the design repeated about the circumference of the tire tread, it being understood that the dashed lines form no part of the claimed design;
FIG. 3 is a right elevation view thereof, it being understood that the dashed lines form no part of the claimed design;
FIG. 4 is a left elevation view thereof, it being understood that the dashed lines form no part of the claimed design; and,
FIG. 5 is a partial sectional view taken along line 5-5 in FIG. 4, it being understood that the dashed lines form no part of the claimed design.