The ornamental design for a sidewallportion of an automobile tire, as shown and described.
FIG. 1 is a front view of the sidewall portion of an automobile tire that comprises my invention;
FIG. 2 is a top plan view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a perspective view thereof;
FIG. 6 is a fragmentary enlarged view showing the details of the sidewall portion defined by cross-section by lines A-A and B-B in FIG. 1 thereof; and,
FIG. 7 is an end view taken along line 7-7 in FIG. 6 thereof.
Broken lines in the drawing figures are used to show unclaimed portions of the tire as well as the border between claimed and unclaimed subject matter, and thus form no part of the claimed design.