A plastic wheel
assembly (122, 222) and wheel mounting sleeve (127, 227) used to releasably secure the wheel (122, 222) onto an axle (123, 223). The wheel mounting sleeve (127, 227) includes an axle stabilizing opening (100, 200) positioned in an end wall (158, 258) of the sleeve which receives an axle outer end or axle stub (199, 299) that supports the axle (123, 223) against lateral loading and stabilizes it to reduce wobble, chatter and vibration. The opening (100, 200) permits visual confirmation of proper section of the axle outer end (199, 299) in the opening (100, 200). A universal axle (223, 223a) is also provided which can be used to couple wheels (122, 222) having shaped axle bores (139, 239) to the axle using wheel mounting sleeves (127, 227), as well as being used to couple wheels (420), having straight or substantially cylindrical bores (439), to the axle using conventional fasteners (450, 461, 470).