Precession of a bicycle wheel

A rotating wheel has every point on its rim circumference travelling at the same tangential speed. However if the axis is allowed to freely rotate, as in the example of precession, then the pull of gravity will effect a greater speed for the downward moving half of the wheel than that of the upward moving half. Which in turn means that the parts of the wheel that have a greater speed will travel a greater distance than those parts with a lesser speed. Hence the precession. So when the wheel rotates in a counter clockwise direction the wheel will precess to the right of the axis. This allows parts of the wheel travelling at different speeds to travel different distances.
Looking at the rotating wheel with the rotation axis pointing out of the page/screen:



As the wheel rotates counter clockwise its direction of precession will be to the right. All rotating points on the wheel experience the same downwards pull of gravity. A and D on the wheel experience the same momentum of equal but opposite horizontal momentum from the rotational speed of the wheel. But B experiences the gravitational pull downwards added to the downwards motion of the wheel rotation forcing it to accelerate as it moves downwards from the top to the bottom of the wheel. Whereas D decelerates as it moves from the bottom to the top of the wheel. As it has the same rotational momentum as all other parts of the wheel, but an opposing gravitational pull downwards that slows it down.
C therefore travels slower and must cover less distance. B travels faster and covers more distance. To compensate, the wheel precesses to the right to allow B to travel farther than C.
Overall the fastest parts of the wheel circumference will be moving to the right at the bottom of the wheel and the slowest parts of will be moving left at the top of the wheel.




The paths of two opposite points on the circumference show that if the wheel precesses to the right at it rotates counter clockwise, the upper part of the wheel travels shorter distances