A hubcap for an aircraft wheel comprises a generally cup-like body for covering, in use, a free end of an axle. A pair of transversely spaced support plates on the loading platform retains and supports each crawler tread on the loading platform, and drives are provided for repositioning the support plates relative to the loading platform perpendicularly to the longitudinal direction into an assembling position in which the support plates project beyond the lateral edges of the loading platform. Water and the specific gas in the gas-containing cleaning water after being used can be reused.