I can't seem to find the video right now
but there was a clip on YouTube from one of Keith Code's videos where he shows a guy with a modified bike proving his point. There is a set of "handlebars" welded to the frame above the real handlebars. Because they are welded to the frame, you can push and pull on those bars all you want without affecting steering. Anyway, Code has the rider hang off the side of the bike while holding on the welded bars, and the bike ends up in the grass on the outside of the corner the rider is trying to negotiate. Do the same with the real handlebars, and the bike darts around the corner of the track as you would expect. Code explains that, when you position your body on the bike, you are in fact pushing and pulling on the handlebars even though you don't realize it, and that pressure on the bars is what initiates the turn. Sure, the bike curves a little with body weight, but not as significantly as I had thought (I've practiced shifting body weight to swerve around obstacles without -- intentionally -- pushing on the bars).
If you think about it, this makes sense. I'm like 170 to 175 pounds bare-*** naked (sorry for that
mental image, everyone!
) first thing in the morning, so I'm *maybe* 190 in full leathers and gear; my bike, on the other hand, is probably over 500 pounds all up. Is shifting my C.G. a few inches to the inside of the turn REALLY
going to affect our combined C.G. very much on a bike that weighs more than 2 1/2 times as much as I do? Sure, it helps, and in gymkhana or on a track, every little bit adds up. However, it seems to me that countersteering, intentionally or otherwise, plays a much more important role than just shifting body weight a few inches.