Spring Rate Conversion

[veilside180sx]

I'm going to compile a quick list for reference of the typical spring rates used. I don't think anyone will be going softer than 250 lb/in.=)

Spring Rate Equivalencies

700 lb/in = 12.5 kg/mm
650 lb/in = 11.6 kg/mm
600 lb/in = 10.7 kg/mm
550 lb/in = 9.8 kg/mm
500 lb/in = 8.9 kg/mm
450 lb/in = 8 kg/mm
400 lb/in = 7.1 kg/mm
350 lb/in = 6.2 kg/mm
300 lb/in = 5.3 kg/mm
250 lb/in = 4.5 kg/mm

For the metric rated Eibach or other springs there is an equation to decipher them.

For instance someone recently asked what their GC metric spring was. Here's the breakdown.
Eibach spring numbers
125.64.75

To get the conversion for this you would multiply the n/mm x 5.714 = lb/in

Similar to the US Eibach springs the first number (125) is the length in mm, (64) is the diamater in mm, and (75) is the newtons/mm.

So this spring is 5" long spring, 2.5", and is 428.5 lbs/in.

Here's a few of the typical spring setups and their distance to coilbind measurements

(Length of spring in inches) (Inside diameter of spring) (Distance to coilbind in inches)

600-250-450 3.51"
600-250-500 3.5"
600-250-550 3.49"
600-250-600 3.43"
600-250-650 3.43"
600-250-700 3.17"

700-250-350 4.24"
700-250-400 4.29"
700-250-450 4.09"
700-250-500 4.06"
700-250-550 3.84"
700-250-600 3.78"
700-250-650 3.77"

[Def]

In case people aren't seeing the pattern - multiply your kg/mm value by 56 to get lb/in.

[SoSideways]

In case people aren't seeing the pattern - multiply your kg/mm value by 56 to get lb/in.

Damnit you beat me by 40 minutes hahaha I thought I'd throw that up here after seeing Veilside180sx made the reference that he made this thread and stickied it.

Thanks for the sticky btw!

[veilside180sx]

You can also multipy lb/in by .0179 or vice versa.

[Epstein]

Want to add the common Eibach spring rates? That would help.

[a_ahmed]

What I used to do was google it just type any conversation rate in google's search

"xxx lbs/inch to kg/mm" and it will convert pretty cool, but this thread will do, but google for deadly precision :P

[McCoy]

I guess that means I'm running 9.8K/7.1K springs on my car

Chris, typically the Eibach springs are in lb/in ratings. The few metric one's that I've had were odd balls as it was... 7.7K, 5.5K, etc.

[SoSideways]

Yeah, guess I'll be running 500lb front and 400lb rear springs, since that's what I'm running now.

[veilside180sx]

Want to add the common Eibach spring rates? That would help.

I'll go through and add some of the popular metric sizes, as I come acrossed them.

[veilside180sx]

I added more material to the listing above.

[WishIHadaSilvia]

Can you please explain coilbind? I googled it and was reading on another forum, but they didn't really explain it just talking about how they were trying to avoid it.

[veilside180sx]

Coilbind is when a spring is completely compressed to the point where the individual coils of the spring bottom out, or compress into each other. A spring cannot compress anymore than that amount.

[Def]

Yep - coilbind = bad. Your spring rate essentially goes to infinity at that point, so you can imagine it makes the car hard to handle at the limit if it frequently does that.

[a_ahmed]

I thought this would be an interesting addition to this thread:

http://www.badlose.com/tech/springrates.html

Different s13 spring rates on different springs/coilovers/etc...

[Umai Kakudo]

Swift has a great PDF spec sheet for their springs that includes rate, usable stroke, max stroke, max load, and weight.

http://www.swiftsprings.com/file/metric.pdf

Nice!