Mike,
I know of at least one case of a Tiger with 600 #/in springs and the owner
claims it "rides like a Buick". I have 425 #/in springs I got from Coil
Spring Specialties about 15 years ago and I find them to be about ideal for
the street, but still OK for the track. I would like to drive the 600 #/in
car for comparison. I suspect that not all springs of the same nominal
stiffness are the same, depending on the source, and I have heard others
say the same.
You draw a comparison between your Mustang and Tiger with the assumption
that they should require springs proportionate to their respective weights.
However, this overlooks the geometry of the suspension. The effectiveness
of the spring is also a function of the position of the spring relative to
the wheel and pivot point, analogous to the mechanical advantage of a
lever. For example, if you move the wheel outboard it has the effect of
softening the springs since you are applying the weight of the car to a
longer lever arm. I don't know the geometry of your Mustang, but it
probably is somewhat different than a Tiger. However, having said this
(and, pardon me, but I just had to), I think you would find that picking
the Tiger springs according to its weight compared with your Mustang to
give you a good result; in fact, using your numbers, it would be the 425
#/in springs I use.
I infer from your comments about "drive and not plow" that you think
stiffening the front springs alone will produce this result. Actually, the
stiffer the front springs relative to the back, the more the car will plow
(understeer). And we haven't said anything yet about sway bars (maybe
later). I would say that the front and rear are very interdependent and if
you change the rates at one end, you should change them more-or-less
proportionately at the other. In the rear you have the choice of buying a
whole new set of leaf springs, or beefing up the stock set. You might want
to consider re-arcing them while you're at it. I had two leaves added,
powder coated and re-arced at E&C Springs in Escondido, CA. They did a
terrific job and I can't think of any single change I've made that has made
such an improvement in the handling of the car. I spent almost all my
energy for many years working on the front suspension to the neglect of the
rear and finally found out just how important the rear is (suspension that
is). You might want to consider adding one beefy leaf just under the main
leaf and extends the full distance front to rear. This will add stiffness
and reduce wind up, although you probably still will want some kind of
traction bars.
I guess the real message hear is that you are opening an engineering can of
worms and there are no quick fixes or magic bullets. Talk to a lot of
people, get yourself some car engineering books, and get informed to some
degree about roll stiffness, roll center, etc. and, starting with your own
philosophy and goals, develop an engineering plan. This would include
deciding whether you want to use sway bars (front and/or rear), traction
bars, Panhard rod, etc., in addition to the springs per se. Once you have a
pretty good idea of your goal, you'll have a lot better chance of getting
there. Take your time and, as the Nissan guy says, "Enjoy the ride!"
OK, everybody back to work, the holiday's over!! ;-)
Bob
At 07:08 PM 9/6/99 -0700, mjb2@home.com wrote:
>i have a question about springs, front and rear for my 65' tiger. since
>i received so many answers about the shocks, i figured i might ask about
>springs. this is not a X-cross car. am i to assume (dangerous word) that
>i want to keep the rear springs as designed by the engineers and
>stiffen the fronts? i see that a front is advertised around 325lbs,
>that is give or take. since my 66' mustang has 480's on the front and
>only weighs 300 pounds more than the tiger and rides quite well,
>wouldn't it make sense to at least apply the same thought. i would like
>to drive and not plow, i live in the city.
Robert L. Palmer
UCSD, Dept. of AMES
619-822-1037 (o)
760-599-9927 (h)
rpalmer@ucsd.edu
rpalmer@cts.com
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