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Save Sk Wasting His Time... Online Spring Rate Calculator

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STATUS Grand Master

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i got sick of doing the same thing on ns.com years ago here are a few good calculator sites. It is a simple calculation.

http://faq.f650.com/FAQs/ShocksSpringRateF...te%20Calculator

http://www.iroczone.com/calcs/chassis.htm

this one will give you a Kg/mm result also

Metric and imperial result

Scandrew Contributor

Scandrew

Posted
Posted (edited)

I've tried calculating it using them but I'm not too sure what measurements they're suppose to be entered as. I assumed in inches (") and tested a few of the measurements in SKs' thread but can't manage to get the same rates as him so I'm not sure if I'm doing it right?

Edited by Scandrew
STATUS Grand Master

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Remmember the above calcs are imperial, i have a spreadsheet i made in metric. here is the equation for those who would like to know how the calcs work so you can make your own.

11,250,000 - Torsional Modules For Steel (Constant)

CSPWD - Coil Spring Wire Diameter (How thick is the wire?)

8 - Constant

NOAC - Number Of Active Coils (Coils that are free to move. Not coils seated. It may be that 1/2 of the top and bottom coil is seated causing a spring with 8 coils to have the distance of 7 free.)

CMD - Coil Mean Diameter (The diameter from center to center of the coil. Measure the diameter of the coil from wire center to wire center. If you know the coil is .5 inches thick and the outside diameter of the coil spring is 3 inches, then the Coil Mean Diameter would be 2.5 inches)

(11,250,000 x (CSWD x 4))

(8 x NOAC x (CMD x 3))

All Measurements in inches - calculate as decimal ie 1/2 inch as 0.5

STATUS Grand Master

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With your calculator and the following measurements I have an end result of 46037.96138.

Wire ID: 11mm (0.433in)

Coil ID: 64mm (2.522in)

Coils: 7

.

did you input inches or mm? it needs to be in inches.

using http://www.racingsuspensionproducts.com/spring%20rate.htm i get 14kg/mm or 794Lb/in

Scandrew Contributor

Scandrew

Posted
Posted (edited)

URAS, you wouldn't happen to be able to recommend spring specs for 4F 3.5R kg/mm rateswould you? :rolleyes:

i.e If I have a coilover currently using a 64mm spring ID, would I be able to use a 61mm spring ID on it?

Edited by Scandrew

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