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; and,
FIG. 2 is a front elevational view of the tire tread shown in FIG. 1.
The broken lines showing the tire inner beads and sidewalls in FIGS. 1 and 2 are for illustrative purposes only and form no part of the claimed design.