A tire-mounting structure, the tire-mounting structure having a laterally extending end wall, two protrusions longitudinally extending from the end wall, the two protrusions spaced apart from one another, and a recess formed between the two protrusions. The recess is dimensioned such that a first distance between the two protrusions at a distal location relative to the end wall is longer than a second distance between the two protrusions at a proximal location relative to the end wall, where the first distance corresponds to a first tire dimension and the second distance corresponds to a second tire dimension, the second tire dimension being narrower than the first tire dimension.