A wheel rim includes an annular rim body that has an annular base wall, a pair of annular side walls, and a stop unit. The annular side walls extend respectively from lateral edges of the annular base wall. Each annular side wall includes a hollow segment and a connecting segment that interconnects the hollow segment and the annular base wall. Each hollow segment has an inner wall portion, an outer wall portion, and a tire bead retaining part projecting from the inner wall portion toward the other one of the annular side walls. Each inner wall portion is adapted for contacting a respective one of tire beads of a tire and cooperates with the stop unit and the respective tire bead retaining part to retain the respective tire bead.