[tech] swaybar question

[jdbubb@ix.netcom.com (Dan Bubb)]

Neal Tovsen wrote:
> 
> Sorry, but no. Higher front springs do not increase roll stiffness if you
> also increase the load applied to them. A 600lb spring with 600lbs on it
> will compress 1 inch. A 300lb spring with 300lbs on it will also compress 1
> inch. Presuming VW made proportional changes to the springs (which they
> probably didn't exactly, but more-or-less), heavier front springs will
> compensate for the heavier engine while maintaining the handling
> characteristics. Swaybars do not carry weight, but they do influence the
> transfer of it. The larger rear swaybar on the 16v makes the car understeer
> less, which is appropriate on a car designed to be more of a "sports car"
> than the 8v was.
> 
The springs create a torque (twisting force) about the roll center as
the car corners. So, you have a spring force acting at a given distance
(moment arm) from the roll center that creates this torque. For a given
roll angle the moment arm distance stays the same. If you increase the
spring rate the force of the spring increases, the torque about the roll
center increases in proportion to the increase in spring rate.
Summary; roll stiffness IS substantially proportional to spring rate.
In practice higher weight coupled with proportionally stiffer springs
will give you approximately the same roll angle as long as the center of
gravity height doesn't change. (and, of course, we all know the 16V
engine has a higher CG! Bad!) But, the amount of weight being carried is
greater (less grip) and the amount of weight transferred is greater due
to the higher roll stiffness. (less grip)
I'll stand by my original anaylsis.
Dan