writes:

That the bicycle does not steer when
stationary shows that effect as well. TO make the bicycle steer
merely from rake and trail takes a large lean angle and does not
accomplish the same effect.

OK, I have just been out to the bike shed and carried out an empirical
experiment; and this is just false. My observations are, when stationary:

(i) On rougher surface (grass), greater lean angles are required before a
steering effect is noticed as compared to smoother surfaces (tiled
floor).

(ii) On tyres with a larger contact patch (mountain bike), greater lean
angles are required before a steering effect is noticed as compared to
smaller contact patch (road bike).

(iii) All bikes on all surfaces showed steering effect on lean.

(iv) Road bike on tiled floor showed to within the limits of
observational measurement as much steering effect on the same amount
of lean when stationary as when moving.

(v) By contrast, a mountain bike on grass had to be leant to a
considerable angle to show any steering effect when stationary, and
when the steering effect did occur it occured in jerky movements
through considerable angles.

From this I conclude that the resistance to steering when stationary
is as much due to friction at the contact patch as anything else (and,
lets face it, tyres are designed to generate the maximum possible
friction at the contact patch).

I'm quite prepared to repeat the experiment on camera an post a
quicktime movie. But it's a very simple experiment and I'm sure
everyone else can repeat it too.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

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