Why doesn't the bike fall on its side?

The construction of a bicycle is pretty simple, and it seems that it has long been understood how and why a two-wheeled vehicle maintains excellent stability. It has always been believed that two mechanisms play the most important role in maintaining the balance of a bicycle. The first is automatic steering, or the castor effect: if the bike leans in one direction, the front wheel turns itself in the same direction, after which centrifugal force returns the wheel to its original position. The second mechanism is associated with the gyroscopic moment of the rotating wheels.

American engineer Andy Ruina and his colleagues decided to refute both of these statements. They designed a bicycle similar to a scooter, in which the front wheel touches the support in front of the point of intersection with it of the axis of the front fork, which "cancels" the effect of the castor. And besides, the front and rear wheels are connected to the other two, rotating in the opposite direction, and thereby nullifying the gyroscopic effect.

However, this bike doesn't fall over on its side that quickly. In fact, it keeps the balance no worse than a conventional bike and even demonstrates the same automatic steering. Based on the results of the experiment, the authors concluded that both effects - both the castor and the gyroscope - play an important role in maintaining the balance of a riding bicycle, but both are not critical for it.

It is not completely known why the bike does not fall. According to the latest assumptions of engineers, a special load distribution plays a key role in this.