It was written above that the purpose of countersteering was to get the front tire's contact patch out from under the bike's center of gravity so the bike would lean into the turn. True. If the bars are steered into the turn centrifugal force will fling the bike and rider off into the weeds on the outside of the turn. But.....if the bike is going slowly enough so the centrifugal force is very minor, the turn can be accomplished with shifting of body weight and just turning the bars into the turn. This is why we see some lower speed limits for countersteering. It isn't about the speed per se, it is about handling the various forces at the speed we're running.
We don't countersteer to maintain a straight run, but our bike's front suspension geometry is doing it for us. This is the purpose of trail--constantly self correcting steering. The front end is always oscillating to hold us on an average straight course. We can counter to start a mild turn just by light force to prevent the trail correction to one side.
With the knowledge that every single track vehicle needs to be countersteered to turn it, it is interesting to watch "non-countersteerers" make turns. I saw one guy who started each turn with a head lean into the turn, then his shoulders followed, then his arms followed the shoulders, and unknowingly he countersteered. Others use the body weight shift or shoulder shift and end up with their arms pushing the bars to countersteer while they insist that the whole concept is bunk.
About learning any movement---research has shown that it takes several hundred (correct) repetitions of a movement to create the new neural connections in the brain to "learn" the movement and make it automatic. Until then we have to think to make the movement which is slow and tiring, and two things can not be thought of at the same time. It takes several thousand repetitions to change a movement, to re-learn, to change a bad habit. If one understands why intentional countersteering with the hands must be used for very quick corrections, then it can be realized why it must be practiced to learn. And, practice countersteering harder to tighten a turn as well as pulling back on the inside bar to widen the turn--both may be needed to miss an obstruction.
A bicycle needs to be countersteered, of course, but it is so sensitive that very little countersteering effort is needed, plus the ratio of rider weight to bike weight makes rider weight movements more significant. I most notice the countersteering when I'm coasting on a straight downhill with a turn ahead. No other movements are needed to turn except a brief slight pressure forward on the grip to the inside of the turn. There are some rural areas in Europe where they have old style bicycle type riders on sliders for the winter. No wheels. These must be countersteered as well.
Gyroscopic precession (not procession) takes part, but I still don't understand if precession is a force to turn the rotating wheel if the axle is tilted, or if precession tilts the axle when the rotating wheel is turned.
It's not what you look at that matters, it's what you see.
Henry David Thoreau
PT Rider screwed with this post 01-21-2013 at 12:39 PM