1, Measure the coil wire diameter accurately (use vernier calipers or
micrometers) of both the new springs and your stock ones. You get "d1" and "d2"
2. Count the number of coils in each spring, and subtract 1/2 a coil. You get
"n1" and "n2"
To a first-order approximation, the relative stiffness of spring set 1 to spring
set 2 is ((d1/d2)^4 ) * (n2 / n1).
The spring rate is proportional to the fourth power of the wire diameter, and
inversely proportional to the number of coils.
I ignored the effect of reducing the helical diameter, since it (hopefully)
didn't change very much.
You can figure out how much the car will settle onto the new springs (again,
approximately) by measuring the stock spring installed on the car with the car
on the ground. Then if you subtract that from the length specified in the
manual, you know the amount of spring compression. The heavier spring will
compress less in proportion to how much stiffer it is. Combined with its shorter
initial length, you may end up with nearly the same ride height.
Example: Spring 1 has a free length of 10" and a compressed (on the car) length
of 6.5". Spring 2, which has twice the rate as calculated above, has a free
length of 8". Since it's twice as strong, it will only compress (3.5/2) = 1.75"
under the same load, giving a loaded length of 6.25". So the car will sit about
1/2" lower (the springs sit about halfway out on the control arm).
I could go dig through a bunch of reference material if you want precise numbers
and equations. I would guesstimate that you could run 50% stiffer springs
without turning the car into a real kidneybuster, but that also depends on the
tire size and aspect ratio you run.
Theo Smit
tsmit@novatel.ca
B382002705
> -----Original Message-----
> From: Mike Burd [SMTP:mikeburd@email.msn.com]
> Sent: Monday, January 11, 1999 2:20 PM
> To: Tiger Questions
> Subject: Springs
>
> I am finishing a project someone else started. They obtained front springs
> for it that are a much heavier coil but the same outside diameter. The
> spring length on the bench is almost 3 inches shorter than what the manual
> says is the correct length for stock springs. The previous owner says he was
> told, where he purchased them in England, that the originals were soft and
> with the 302 these stronger springs would make it handle better but have
> little effect on the handling. Does anyone have any experience with these
> heavier shorter springs. Will it effect the height of the car?I don't mind
> it a little harder ride but my wife and I plan on traveling in the car and I
> don't want any complaints. Thanks Mike mikeburd@msn.com
>
>
>
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