Yeah, OK, and I have no problem imaging such a vibration... I am imagining it as the wheel precessing (wobbling) at very high speed around the axle. Seen some crazy thing happen and any small change like axle clearance could effect it, or so it seems. And the higher wheel speed with the bigger core or smaller wheel makes total sense.
Just a side story, which made me not doubt anything like that : In testing of a certain naval electronic cabinet for high shock (simulating a torpedo hit on the ship), an electronic card would be found lying outside a completely closed cabinet after the test. High speed film showed the cabinet door bowing out during the test and the card would coming flying out of the gap between the momentarily bowed door and the cabinet opening. You could never design anything to do that LOL