The ornamental design for a tread portion of an automobile tire, as shown and described.
FIG. 1 is a front view of a tread portion of an automobile tire showing the new design, it being understood that the tread pattern repeats uniformly throughout the circumference of the tire;
FIG. 2 is a perspective view thereof;
FIG. 3 is a left side view thereof, the right side being a mirror image thereof; and,
FIG. 4 is a fragmentary enlarged view showing the details of the tread portion thereof.
The broken lines in the drawing figures are for the purpose of showing environmental structure only and form no part of the claimed design.
The broken lines showing the area between the tread portions is for the purpose of illustrating portions of the tire and form no part of the claimed design.