Why is it easier to balance a bicycle while it’s in motion?

Question

I never quite understood why it is so much easier to keep a bike balanced while riding at a certain speed, compared to riding it really slow, or while standing…

In: 540

Answer 1

Here’s the answer I gave to this question earlier:

There are four major things that keep a bike upright.

One is that the rider on the bike is active, constantly steering to keep the bike beneath them, and constantly adjusting their weight to balance the bike. You can design a bike as you like, and a human rider will be able to learn to ride it.

The second is that the front wheel forks bend forward. This puts weight of the front wheel ahead of the steering pivot. So if the bike leans in one way, the wheel will tend to ‘fall’ in that direction, steering the bike into the lean and correcting it.

The third is that the front wheel’s contact patch is behind the line of the steering pivot. If the bike is pushed sideways, this push will cause the front wheel to steer away, rebalancing it.

These three effects all require the bike to be moving, so the movements of the steering wheel affect the motion of the bike to rebalance it.

And the fourth is a gyroscopic effect on the front wheel. It’s complex, but if you take a wheel spinning on one axis, make it turn in another, the result will be a force 90° later, in the third axis. For a bike’s front wheel, it means if the bike leans in one way, you get a force tuning the front wheel to steer into the lean and counteract it. Like the first three, this needs both a spinning wheel, and a moving bike, for it to work.