Some additional thoughts on the "tricycle" problem. If the rear wheels are the drive
wheels they will not be pushing (the tangential force) on the CM of the tricycle as it
moves through the curve. Because the wheels must "slip" a little at least to go around
the curve (I'm imagining a curve to the left) the wheels will have a force that is
directed to the right of the CM, causing a torque around the CM of the tricycle (counter
clockwise in the vertical direction, looking down on the tricycle). Of course there will
be another torque around the horizontal CM of the tricycle (clockwise for a "left turn")
because the tires are not acting directly through the CM - this is why the tricycle might
"tip over" or why a bike must "lean into" the turn.
(Last day of the grading period so I have time to ramble on - sorry for the big
bandwidth.)