Hey folks -

Who says we can't have interesting on-topic discussions
here at ARBR? For starters, I recognize that many
cyclists may feel more at ease on a two-wheeler at high
speed than on a trike. I think one of the reasons for
this is that it's a fairly simple learning process for
us to make controlling a bike with subtle leaning and
weight shifts pretty much instinctive, and most of us
learned it long ago when our brains were young and wide
open. Another reason is that unlike a trikey at low to
moderate speeds, a biker is ALWAYS required to
continuously interact with his cycle, even though it is
a largely subconscious process. There's not much in the
way of a transition from riding a bike at 12 MPH to
zipping along at three times that speed.

Chalo wrote:

Trikes as a rule have a natural "critical speed"... as
speed increases, the weight shift becomes more sudden
and eventually causes a violent response to even mild
steering inputs, up to and including high-siding the
trike.

While I can appreciate most of chalo's comments, this
bit seems to me to be what a logics professor might call
'A giant leap from a fallacious assumption to an
erroneous conclusion'. ;-) What exactly is this strange
"weight shift" and why would it become "more sudden"?
A well-designed stiff tadpole with an experienced, even
modestly talented rider doesn't go through some kind of
radical transition (like an aircraft at Mach One) so
that it begins to provide a "violent response" to his
control inputs.

The front end geometry of a tadpole is pretty much the
same as an automobile's, and as far as I know, there's
no such thing as a "critical speed". Of course, with
good lateral traction a driver can roll a Miata, just
as a rider can roll a trike. Speed plays a big role in
rollover susceptibility, and tadpoles have comparatively
sensitive steering, meaning: the front wheels turn much
farther for a one-inch movement of your hands on the
bar than on an auto. At higher speeds, small steering
inputs cause higher lateral acceleration than at lower
speeds, and of course it takes a smaller jerk of the
bars to flip a trike at 50 MPH than it does at 5 MPH.

One simple fact of cycle dynamics, however, is that a
trike is inherently very stable in the roll axis at
any speed, even parked. A bike, meaning a vehicle with
two tires on the same lateral axis, has no - ZERO! -
long-term roll stability. It wouldn't be a very serious
engineering challenge to implement a stone simple
servo-controlled single-axis automated steering system
for a trike, using an airplane type gyro, so that it
would roll down a hill in a straight line. I won't stay
up waiting for someone to do that with a bike...

The biggest single difference that I see between bikes
and trikes is that anyone riding a two-wheeler has to
constantly make minor steering and/or weight shift
corrections to keep the bike upright AT ANY SPEED, and
the process of making those continuous compensations
becomes almost subconscious for him. The process is made
a bit more appropriate to normal human aptitudes by the
short-term stability provided by the precession effect
of the wheels and the rounded profile of bike tires.
But on a trike, at low and medium speeds, there is
absolutely no need for the rider to do anything but make
minor steering corrections. When the trike begins going
fast enough to make it more of a challenge to control
its direction with its sensitive steering, compensating
and correcting for stiction, linkage slack and
hysteresis, it begins to demand a lot more in the way of
attention, precision and good reflexes. If that seems to
set some kind of "critical speed" for the trike, or to
give it a Jekyll-Hyde nature, it's probably a good idea
to remember that the real difference from a bike is that
a bike is always in the Hyde mode.

I've used the analogy before, but if you put a big
long-stroke steam engine pumping the pedals on a trike,
and send it off down the road, it may go in the wrong
direction, and it may waggle back and forth, but... if
you do the same thing on a bike, it most likely won't
make it out of shrapnel range before it falls over and
explodes!

Regards,
Wayne