The ornamental design for a center tread for a tire, as shown and described.
FIG. 1 is a perspective view of a center tread for a tire showing our new design, it being understood that the pattern repeats uniformly throughout the circumference of the tread;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a right side elevational view thereof; the opposite side elevational view being identical thereto; and,
FIG. 4 is an enlarged fragmentary front elevational view thereof.
In the drawings, the broken lines defining the shoulder tread, sidewall, inner bead and the peripheral boundary between the center tread for a tire and the sidewall are for illustrative purposes only and form no part of the claimed design.