Working out spring rates?

[drft86]

Hey all

Just wondering if anybody could give me some insight on how i can work out my spring rate.

Coilovers from jap, but the car was very very under steery since i oput them in. So I'm thinking there bit to stiff?

Thanks guys

[rthy]

are you willing to take one of them out to do a check?

[drft86]

of course

[rthy]

ok this is rough but it will do:

get the spring out and measure the free height, then get one of your heaviest friends to put all his weight on a spring as evenly as possible, measure the compressed height and then measure his weight.

Divide his weight in KG by the difference in mm that the spring compressed to find out the rate in kg/mm

[johl]

ur infinite knowledge amazes us all Sam_Q

[drft86]

ok, thanks mate

[verm69]

<div class='quotetop'>QUOTE (johl @ Mar 10 2008, 10:02 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=499634)</div>
ur infinite knowledge amazes us all Sam_Q[/b]

ditto... how do you know this shit? it's like your a 50 yr old rally pit mechanic stuck in a young guy's body :lol:

[rthy]

hahaha you guys crack me up, I am not some amazing guru I am just good at remembering things sometimes.

I read it somewhere about 6 years back, maybe autospeed?


heres a simplified formular I have come up with:


kg/mm = weight / (free height- compressed height)

[blair]

baha ghettoest/easiest method!

[redsprinter]

example please for the noobs or for people like me who failed in maths .

[blair]

measure spring = 200mm

stand on spring and measure = 190mm

measure yourself = 60kgs

divide 60 by (200-190)
= divide 60 by 10
= 6KG/mm

[Jonny Rochester]

I put a spring rate formula up probably only 2 weeks ago. But Sams way is simpler and probably even more accurate in some ways.

Fat guy = 100kg

Spring goes down 12mm

100 / 12 = 8.3

The linear spring rate is 8.3 kg/mm

[ke70dave]

if you really want to know where it comes from, its the basic spring formular

F=K*X

where

F=force (your fat guy)
K=spring constant (your spring rate)
X= distance moved under the force

keep in mind that you need to keep your units need to be right

F =kg
X= mm

will result in a value of K in kg/mm

you can re-arrange the given formula to give whatever value you like

in our case it becomes

K = F/X (fat guy weight/distance travelled)