The ornamental design for a tread portion of an automobile tire, as shown and described.
FIG. 1 is a perspective view of the front and left side of a tread portion of an automobile tire, it being understood that the tread pattern repeats itself uniformly throughout the circumference of the tire, showing my new design;
FIG. 2 is a front elevational view thereof, the top plan, bottom plan and rear elevational views being identical thereto;
FIG. 3 is a left side elevational view, the right side elevational view being a mirror image thereof;
FIG. 4 is an enlarged fragmentary front elevational view thereof; and,
FIG. 5 is a cross-sectional view taken along the line 5—5 as shown in FIG. 4 thereof.
The elements shown in broken lines are for illustrative purposes only and form no part of the claimed design.