>Nor Meyer <norbikes@gmail.com> wrote:
> I recall reading somewhere (Jobst...?) that the bicycle's geometry is
>designed to "encourage" the front wheel to return to a "neutral"
>position---that is, in line with the frame----whenever it's steered away
>from the neutral/forward position. The reason for this is that anytime the
>fork is turned from the forward position it imperceptibly raises the front
end of the bike, thereby raising the potential energy of the bike & rider.
There must be a misunderstanding: The front of the bike lowers - not
rises - when you turn the handlebars. That is what wheel flop is! (I
doubt Jobst would have written something so plainly wrong.)
>The forward/neutral position for the front wheel/fork therefore represents
>the most stable position, towards which the bike is naturally inclined----
provided the fork can rotate freely in its bearings.
Alas, it is the least stable position - the bike really is balanced on the head of a needle. And bikes with too much wheel flop feel that way - they will dart off to one side or the other when you look over your shoulder or reach for a water bottle.
You can visualize this: Take a bike, put it on the floor, orient the front wheel straight, and then wiggle the saddle slightly. The front wheel will turn. (If the straight-ahead position was the position of the lowest energy, the front wheel would not budge.)
Fortunately, there are other factors at work that stabilize the bike. The handlebars do tend to return to straight-ahead when you ride, but that is a function of trail and the gyroscopic forces of the front wheel. (When stationary, neither of those are effective, which is why the bars tend to turn.)
Good headset bearings still are important, because you constantly move the bars a fraction to balance the bike. You don't want to overshoot... and then overshoot the other way, etc., going along is a series of swerves.
Jan Heine
Editor
Bicycle Quarterly
140 Lakeside Ave #C
Seattle WA 98122
http://www.bikequarterly.com
>
>Hence the necessity of
>properly adjusted headset bearings----needle or ball----for care-free hand's
>off riding. Which, incidentally, allows the rider a superbly nuanced
>interaction with his/her machine....
>
>Nor Meyer in Iowa