Is countersteering required to change direction or can you "lean" to change direction without countersteering?

[moorepants]

Description

It is clear that if you only have steering input to a bicycle that you must countersteer* to change direction, i.e. steer first left, then right to go right. If you ride without hands and let the steer be free you can still change the direction the bicycle travels with a variety of "body language". For example you might say you can lean left or right to change the travel direction. Or you can shift your knees left and right to affect the direction of travel. There are a couple of questions that don't really have definitive answers regarding non-steer control inputs.

1. Can you change the direction of travel while riding no-hands without countersteering occuring?
2. Can you change the direction of travel while riding hands-on without countersteering occuring?

One piece of evidence I have that points to the answer of #1 is this figure:

from Hess, Ronald, Jason K. Moore, and Mont Hubbard. 2012. “Modeling the Manually Controlled Bicycle.” IEEE Transactions on Systems, Man, and Cybernetics - Part A: Systems and Humans 42 (3): 545–57. https://doi.org/10.1109/TSMCA.2011.2164244.

If you take the Whipple-Carvallo model and control it with a roll torque only (torque between rear frame and ground about roll axis), it seems to require an ever so slight countersteer. A roll torque isn't exactly the torque one would generate between the rider's torso and rear frame, but I think it is effectively the same.

To answer the question we'd need to demonstrate changing direction without countersteering (or find someone who has).

*there is at least one other definition of countersteering: in a steady turn you may have to apply a steer torque in the opposite direction of the steering to maintain the steady turn.

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