The ornamental design for a tread of a tire, as shown and described.
FIG. 1 is a perspective view of the tread of a tire of the present invention, it being understood that the pattern is repeated uniformly throughout the circumference of the tread,
FIG. 2 is an elevational view of the tire tread shown in FIG. 1,
FIG. 3 is a right side view of the tire tread shown in FIG. 2; and,
FIG. 4 is a left side view of the tire tread shown in FIG. 2.
The broken lines showing the tire inner bead and sidewall in FIGS. 1, 2, 3 and 4 are for illustrative purposes only and form no part of the claimed design.