system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it easy to balance on a bike/motorcycle that is in motion opposed to one not moving?
gpt
A common answer is the spinning wheels act as gyroscopes-- *effectively* increasing inertia so a standing object resists falling over (or even starting to tip). That's not the whole story.

The geometry of bicycles and motorcycles means that leaning them causes them to steer. Gyroscope effects are sometimes mentioned here too, but it has a *lot* to do with the shape of the tire. The edge is shorter, and therefore moving slower, than the center of the tire. When leaned, the center wants to cover more ground and "catch up" with the side of the tire. This causes the bike to turn.

The turning of the bike makes it straighten up, due to a moving object's tendency to keep moving in a straight line (when turning, it leans to the outside of the curve). Once it straightens up, it stops turning. So you might notice a small deviation from a straight line but it's not going to continue turning. The correction is self-limiting and when you're moving these "corrections" are so quick and constant it just feels like a force or natural tendency for the bike to stay upright.