roll centers

[Peter Kemos <peterk@domain.elided>]

Hey, don't let this thread die yet, lots of good discussion and
information.
Here's a question which Fred Puhn's book does not specifically address:
How does one calculate front roll center on a double A arm suspension
where the lower A arm is NOT parallel to the ground, but rather angles
upward from the chassis to the hub/spindle/wheel assembly?  All of
Fred's examples have the lower A arm parallel to the ground.

Extrapolating from his examples, the upward angled lower A arm would
locate the instantaneous roll center quite high up on the vehicle, at
approximately a height of the top of the tire.  If one were then to
connect this point with the tire contact patch on the same side of the
vehicle, it would result in a roll center well below ground level.
If on the other hand one is supposed to connect the instantaneous point
with the contact patch of the tire on the opposite side of the car, it
would result in a relatively higher roll center (well above ground
level) than if the lower arm were parallel.

Does this make sense to anybody?
Could anyone please comment?  The car specifically is a 115 series GTV.

Thanks,
Peter Kemos

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