How do i find out the rate of my springs???

i need help. i have a 54 chevy that i am trying to lower. i already have dropped spindles so I'm working on lowering the back a little bit. the cars frame is from an early 1980's monte carlo. i do not know the exact year. I'm guessing the springs came with the frame. the springs are tapered. my plan is to just buy a smaller set of tapered springs but when i called Speedway they wanted to know the rate of the springs that i have now. How do i figure that out?? thank you

 

Ask someone who races cars. They will usually know of a local shop that has a press they can use to rate springs. You used to be able to get spring rates from GM if you can read the tag or if it has a number stamped into it.

 

Put a spring on a flat surface and place a 100 pound weight from your weight lifting set on it.......measure the deflection (compression), figure how many 100 pound weights it will take to get one inch and you will have the rate in pounds per inch.

 

Most race springs are real short and passenger car springs (even cut down) are too long for the checker, but worth a shot. I've used a similar method using a known-weight and measuring the deflection.

Bob

 

<table border="0"><tbody><tr><td valign="MIDDLE" align="CENTER">spring rate =</td> <td valign="MIDDLE" align="CENTER">
modulus of spring steel X wire diameter⁴
--------------------------------------------------------------------
8 X number of active coils X mean coil diameter³

</td> </tr> </tbody></table> modulus of spring steel = 11,250,000 pounds/inch² = 78,500 newtons/millimeter²

 

Or, http://www.pontiacracing.net/js_coil_spring_rate.htm

 

This thread deserves categorisation (technical). That way, it would be easier to find in a search.
Handy thread, thanks..