The ornamental design for a rear shockabsorber for a bicycle, as shown and described.
FIG. 1 is a top front perspective view of a rear shock absorber for a bicycle that is arranged and configured in accordance with a preferred embodiment;
FIG. 2 is a right side view of the rear shock absorber for a bicycle of FIG. 1;
FIG. 3 is a front view of the rear shock absorber for a bicycle of FIG. 1;
FIG. 4 is a left side view of the rear shock absorber for a bicycle of FIG. 1;
FIG. 5 is a rear view of the rear shock absorber for a bicycle of FIG. 1;
FIG. 6 is a bottom view of the rear shock absorber for a bicycle of FIG. 1; and,
FIG. 7 is a top view of the rear shock absorber for a bicycle of FIG. 1.