How can a motorcycle racer tilt the bike if Newton's third law makes the net force zero?

[rcgldr]

In the case of an unexpected decreasing radius turn, if you've already body steered to lean into the original turn, and you're now hanging off the inside of the bike in a turn, how do you "body steer" any further in order to increase the lean angle?

You just keep shifting more weight over and farther down.

The assumption was the rider was already hanging off as much as possible before encountering the unexpected decreasing radius turn, so more weight can't be shifted over.

Ride standing and leaning forward just enough so that you can keep a light touch on the bars to hold a steady throttle, with your weight balanced on both pegs. Keep your knees out a bit, so there is no contact with the tank, seat or side panels. Now lift your left foot off the peg, transfering all of your weight to the right peg. What happens? Which way does the bike lean, and what do the bars do (and not do)?

The bike leans right, the front tire turns right, and the rider leans left.

 

[berkeman]

The assumption was the rider was already hanging off as much as possible before encountering the unexpected decreasing radius turn, so more weight can't be shifted over.

Ah, no. For regular turns, even at reasonable speed (like offramps), you just end up with the middle of your butt on the inside edge of the seat. When I need to tighten up the turn, my butt slides more off the seat and down the inside of the bike some. For either countersteering or body steering, you'll only end up way down the side of the bike when you're pulling a high lateral force (like in racetrack turns).

Fred at Reg's CLASS school had a great line that he liked to use in the classroom sessions. He talked about trusting your tires, and how to handle getting into a turn hotter than you expected. He used to say, "Just lean more, just lean more." He was referring to putting more and more weight on the inside peg, pulling with the outside thigh, and getting lower and lower. It's definitely helped me a few times

 

[rcgldr]

He used to say, "Just lean more, just lean more." He was referring to putting more and more weight on the inside peg, pulling with the outside thigh, and getting lower and lower.

Except that putting more weight on the inside peg corresponds to the rider leaning outwards and now the turn is is no longer coordinated if no countersteering occurred. Going back to your previous post, if you're standing on the ground, and you lift your left foot, you lean (fall) left. If you're standing on two scales, and you partially lift your left foot so the left scale shows less weight than the right scale (which now shows more weight), you also lean (fall) left.

 

[JeffKoch]

Did you watch the video of Reg at VIR? He uses body steering exclusively.

He most assuredly does *not*, even if he thinks he does and says he does. This is part of the problem with this topic, professional instructors tossing around terms like bodysteering and countersteering aren't being precise and are winding up misleading people. What he really means is that he's achieving a flowing style using his body and arms where he doesn't deliberately and consciously blast the bars with his arms, he does it smoothly and imperceptibly.