--- mark holbrook <rolling_rock_12@yahoo.com> wrote:
> ... As for the front springs I am
> looking for a way to get lower stiffer springs.
> Does
> anyone know where (and how much) I can get these
Mark,
We are lucky that our cars use a 'standard' racing
spring size, 2 1/2" ID.
Look in any racer supply book, Pegasus, Coleman,
Truechoice, etc. and you will find tables of springs,
made by Eibach, Suspension Spring Specialists,
Hypercoil, etc. These are specified by spring rate,
and free length. Prices typically range from $45-90
each.
The trick of course, is to find the combination of
rate and free length that you need.
The spring data for a Mk II (from the shop manual) is
150 lb/in, free length 12.59", fitted length of 7.8",
fitted load of 718 lb.
(free length - fitted length) * rate = load
Note that the load is not the amount of weight on that
wheel, but the pressure exerted by the spring on the
spring seats, due to suspension linkage angles and
geometry.
But the factory springs varied over the years, and
spring settling and actual weight loading affect the
actual ride height.
For your own car, first decide what ride height you
want. Start adding weight (friends/bricks/bags of
manure) until you get the height you want. Open the
hood, and measure the fitted length of the spring. You
will probably want a somewhat stiffer rate than 150
lb/in, maybe 200 or 225.
Here's a problem though. How do you choose the right
free length without knowing the load?
We could use the factory figures, but I suspect that
in the real world, with later cars, the numbers are
somewhat higher
One way is to remove the spring, measure it's free
length, load it with a known weight, measure it's
loaded length, calculate the spring rate, and then
plug into the formula (using the normal fitted length,
not the length with extra weight added) to get the
actual current spring load.
Anyone have a method or formula for doing this without
removing the spring?
In choosing a spring, I would suggest erring on the
short side, ie, the car rides a little lower than you
want. This, since it is easy to add spacers at the
spring seats to raise the height (the factory did
this), but impossible to lower it more.
Of course, some would say to err on the high side,
since the car will settle a bit over time. YMMV
Sorry to be so long winded, but the parts to do what
we want are out there, we must find a way to determine
which ones we need.
Thanks,
Carter Shore
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