I was riding along a country road and decided that I needed something out of my right hand saddle bag. Not wanting to let go of the throttle which is on the right bar, and not having a throttle friction damper, I crossed my left arm to the right and grabbed the throttle with my left hand, then I reached back with my right hand toward the bag. I immediately started drifting to the right due to the shift in weight. To correct for the drift to the right I pushed forward on the right bar with my left hand. Much to my surprise the motorcycle veered to the right. I managed to assume the proper riding position and regain control before going into a deep ditch. This little episode scared the bejabbers out of me. As I rode on slowly and eventually calmed down, I began to realize that something strange had happened. This counter-intuitive event prompted me to perform a little experiment. I turned the bars to the right or clockwise and the bike went to the left. Turning the bars to the left caused the bike to go to the right. This result was not exactly intuitive to me at the time. In both cases the motorcycle, in addition to changing direction, also leaned in the direction of the turn without a move on my part except to apply pressure on the bars.
A few years later while attending the mechanical engineering school at Purdue I delved into the geometry and dynamics of bike handling and discovered some facts. One fact is that an increase in the rate of forward motion results in increased stability due to Gyro scopic effects resulting from front wheel rotation. Secondly, steering is affected by gyroscopic forces as well as by the change of location of the contact patch between tire and road as the bike is leaned or the bars rotated. I call this phenomina, "Counter Steering". That's as far as I want or care to go to stimulate curiosity about this phenomenon. As my engineering books often said when things got complicated: 1. The solution of the problem is beyond the scope of this text. or 2. The thoughtful reader may want to pursue the problem solution him/her self.
At this point I have to add some qualifications to the above. At low speeds when you are making a relatively tight turn, the rider accomplishes the turn by a combination of leaning and steering in the direction of the turn and also by pedal pressure. In this situation dynamic effects on steering and balance are negligable. You may want to experiment but be careful. At a speed of 10 to 15 mph, steer gently in one direction and note the results, then steer the opposite direction and note the results. I say in my essay; "The Bicycle", that a bicycle looks simple but most decidedly is not. If you perform the experiment you will be convinced of the truth of that statement.
What good is it to know this? Have you ever ridden near the edge of the road or some other obstacle and try as you might to shift your balance, you couldn't avoid crossing that line or going over that edge? As a result of several mini-strokes some years back. I tend to drift to the right, (I could never ride a pace line). I have been in the situation where there was a slight drop-off at the side of the road and I fell hard with what the motorcyclists call a tank slapper. I did an endo and landed on by head with the bike on top of me. You can try to shift your balance away from the obstacle to no avail. There is something you can do in that situation and that is to turn the wheel into the obstacle. It doesn't take much so be careful and don't try to shift your balance at the same time. Give the bike its head when you counter steer and let the bike do its thing. Try it sometime. A good way to experiment with this tactic is to ride along the white line at the side of the road and practice steering away from it using the handlebars rather than a change of balance. You just might save some skin someday.
I welcome your comments
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