Richard,
The fact that only the bottom leaf is firmly attached to the diff is
what accounts for the lean. Since all the weight of each side is
supported by that single leaf, the driver's weight tends to distort that
side. While the other leaves above the pivot pin do move left and right
to provide the function of the swing spring, it is the bottom leaf that
distorts and causes the lean.
Joe
-----Original Message-----
From: Gosling, Richard B [mailto:Richard.Gosling@atkinsglobal.com]
Sent: Wednesday, April 14, 2004 8:48 AM
To: 'Joe Curry'; 'Zahid Ahsanullah'; 'Spitfires'
Subject: RE: Driver side lean
While I have a great deal of respect for Joe's knowledge and skills with
a
Spitfire, his answer seems to contradict my engineering understanding of
Spit swing-spring suspension.
Surely the point about the Swing Spring is that it has very low roll
stiffness. The load is taken at the centre of the spring, so there is
little scope for one side to be weakened more than the other - if one
side
was weaker, the spring would simply swing to compensate - which it would
do
without changing the angle of the car (very much).
Almost all the roll stiffness comes from the front of the car.
Therefore,
to correct a lean, you need to replace the front springs and sway-bar -
or,
to adapt Joe's suggestion, swap the springs side-to-side and turn the
sway-bar over, to move the lean to the passenger side, so that your
weight
will counteract the lean once you are in the car.
Alternatively, a popular quick-fix is to fit gas shock absorbers, which
can
be adjusted to add ride height on one side and not the other.
BTW, I have heard people say that their Spit leans to the drivers side
at
the rear, which is why they immediately leap to the conclusion that it
is
the rear spring that needs replacing. Unless they have actually managed
to
twist the chassis of their car, it leans exactly as much at the front as
it
does at the rear - it just tends to be more visible at the rear because
of
the styling.
I replaced my sagging rear spring (mainly 'cos I had a contact with a
good
one he didn't need, having designed and built his own custom
suspension),
and while it raised the rear a little, it did nothing to correct the
lean on
my car.
Richard Gosling
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