Originally Posted by dthogey
I seem to have read conflicting advice regarding cornering. Some people suggest keeping your body more upright (perpendicular to the road) and leaning the bike, others suggest leaning your body with the bike like the racers do.
What do you think??
Understand *why* people do different things.
At normal speeds on the street there is NO reason to be either hanging off the inside of the bike, or positioning the body outside of the bike (i.e., maintaining a vertical body orientation).
For 99.9% of riders, in 99.9% of riding situations, keeping the body with the bike AND THE HEAD/EYES LEVEL WITH THE HORIZON AT ALL TIMES! (and looking *way* ahead through the turn at the same time) takes care of cornering.
More detail (not well phrased, but, hey, I'm tired tonight):
Why do like the racers?? First, basic physics on a motorcycle in a corner: For any given corner radius, for any speed around the corner there is a corresponding lean angle. In other words, the combined center of mass of the rider and the bike must be at a fixed position inside of the curve (a position which defines the lean angle) in order to balance gravity's pull of you toward the ground, and the centripetal acceleration (felt as the force trying to throw you out of the curve). You know this is true because when you are leaned over at a fixed speed, the bike neither falls on over to the ground, or stands up and runs off the road -- the center of mass is located right on the line which defines the balance between falling and rising up out of the turn.
If you are cornering so fast that you are starting to drag hard parts of the bike on the ground, you are at the maximum speed you can go on that corner on that motorcycle -- UNLESS you can somehow play around with the bike's and the rider's centers of mass, without altering the combined bike/rider center of mass position.
If in the middle of this spark-generating, bike dragging turn you slide your butt to the inside of the bike ("hang off"), your center of mass goes inside and lower -- that permits the bike's center of mass to go higher (i.e, the bike can lean less) to offset your shift while keeping the combined center of mass in about the same place. Because the bike is no longer leaned over so far that you are dragging bits, you can either maintain that speed to complete the corner without the possibility of the dragging bits hitting something hard and flipping you off the road, or you can go faster, until the bike once again is leaned over far enough to start dragging hard parts again. So, racers hang off because it permits them to obtain the maximum possible speed around the turn by keeping the bike up off the ground for as long as possible.
Any application for hanging off on the street? A couple.
First, you can do it on a twisty road to impress your friends with your killer riding skillz -- all while looking like an idiot because your bike is leaned over all of about 20 degrees. On the other hand, if you really are going so fast on the street that you *need* to hang off while you show off to your friends, you are a total f'n idiot, and hopefully your imminent removal from the gene pool will not involve devestating harm to innocent people.
Second, if you know how to hang off and you've been foolish enough to find yourself in the position of hopelessly overcooking a turn, there's a fantastically-slim chance that when you're suddently dragging hard, you might be able to quickly hang off to the inside and reduce the dragging just enough to make the corner -- highly doubtful, though, as if you're in this situation in the first place the suction from the pucker on the seat will probably have locked you in place while you target fixate, staring at the guard rail or tree you're about to hit, instead of continuing to look through the curve to the safe exit.
You might note that between the sarcasm above two primary nuggets: (i) never ride fast into a turn you can't see through unless you're really willing to run off the road at that moment, and (ii) NEVER look at what you are afraid you are going to hit -- because YOU WILL. You WILL go *exactly* where you are looking, everytime. It takes a HUGE amount of training and self-discipline to not follow the human survival instinct (eyes lock on the big pain threat), but instead to ALWAYS look at the turn exit. If you look where you want to go, the bike will almost magically go there (and you'll be surprised how much more it can lean than you think it can).
As for leaning outward (another way of saying keep your body vertical, i.e, perpendicular to the pavement), the only place for this is in *very* slow parking lot maneuvers -- again, the "why" tells you whether and when to do so: On a motorcycle, the further a round-profile motorcycle tire leans, the more its contact patch with the ground moves up toward the wheel's axle -- the further up the tire, the smaller the effective rotation radius of the wheel. What has this got to do with anything?? At low speed, the farther over the bike leans, the smaller the effective radius of the wheels, and the tighter the turn the bike can do.
Search the web for some of the police motorcycle rodeo videos and note their body position as they execute various radius turns -- the tighter the turn, the more they are letting the bike fall over under them while they keep their bodies upright. Interestingly, they are applying the same principles as the hanging off racers -- for any given turn, for a given speed around the turn, the center of mass must be leaned over toward the center of the turn by a fixed amount. The racers move their center of mass inward so the bike's center of mass can be farther outward (i.e., more upright) -- all the while the combined center of mass stays at the same place, as required for that speed around the turn. In very tight low speed turns, for a desired speed aound the turn, the combined center of mass must be at a corresponding fixed lean angle. If the rider moves his/her center of mass *outward* (staying vertical as the bike leans), then the bike's center of mass must move inward to maintain the combined center of mass at the correct location for the desired turning speed -- and that increased lean makes the tire's effective radius smaller and thereby allows the bike to go through the turn much tighter than if the rider stayed aligned with the bike.