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