Yes, the swing spring is a bit longer. The goal of the modifications to the
suspension was to minimize the jacking effect, inherent in the design of the
swing axle suspension. This was accomplished by a drastic reduction of the
roll stiffness in the rear, an increase in rear track, and an increase in the
negative camber of the rear wheels.
The reduction of the roll stiffness was accomplished by having only some of
the spring leaves contribute to roll stiffness, the rest, free to pivot, only
provide vertical resistance. Overall roll resistance was kept roughly the same
by fitting a much larger front roll bar.
The length of the spring and the axles were designed to increase the track and
add more negative camber while doing so. The most benefit for earlier style
Spits is comes from replacing all the related parts as a package - rear spring,
rear axles and front sway bar. Different, and usually less optimal, results
can be had by replacing only one or two of the items, rather than all three.
And of course, one can throw shock absorbers into the picture as well! For
just tooling around on the streets, using the swing spring, the early short
axles and the fat front sway bar are a decent combination. Hmm, why is a
sway bar the same thing as an anti-sway bar?
Now, if you ever get a chance to see my Killer Spitfire at a VTR meet or
autocross, grab hold of that big roll bar sticking out and see what sort
of roll stiffness that car has!
mjb.
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