Abstract: A battery-powered tire pressure monitor and inflation system which is mounted entirely on or within a vehicle wheel, preferably on the inner surface of a wheel cover. The entire system rotates concurrently with the vehicle wheel, thereby eliminating the need for any interconnection between non-rotating and rotating components of the vehicle. The preferred system also incorporates a centrifugal intake valve apparatus, which remains closed until the vehicle wheel exceeds a minimum rotational rate. The centrifugal intake valve closure apparatus thereby prevents fluids or particles from being drawn into the compressor.