A toy gyroscope contains a rotating wheel. If you put it on a stand the axis moves in a circle. Why? The gravitational force pulls down on the center of mass of the wheel. Thus the gyroscope begins to rotate downward. The effect of this new torque is to cause the axis to change direction; to precess.

Precession is also important for bicycles and motorcycles. If the cycle starts to tip to the right, then the rotating front wheel’s axis will rotate, and the wheel will turn to the right, helping to keep the cycle from tipping over.