Fakie wheelie anyone?

Of course I'm not sure :-) I thought it would spin backwards in both cases, but I dind't know, that the force of inertia is stronger than the force of gravity (hope my english is english enough) - never really observed the behaviour, as I don't do tricks. I'm sure you know more in this matter, so I'm not going to argue.

Gravity is not an issue in a (even moderately) balanced wheel.

When you move in one direction your wheel (top) will rotate in the direction you are moving. Lifting the wheel into the air will see that wheel continue to rotate in that direction.

1) If you are going forwards - the top of your wheel will move forwards when the wheel is on contact with the ground - loft the wheel into the air and it will continue in that direction (until the inertia is gone).

2) If you are cycling backwards - the top of your wheel will move backwards when the wheel is on contact with the ground - loft the wheel into the air and it will continue in that direction (until the inertia is gone).

. . . . if you record scenario 1) (bike going forwards) and play the video backwards - the wheel (top) will now be going backwards - just like it would be if you actually were cycling backwards . . .

. . . ie: it is no indication of post production / video trickery.