Trying to identify what spring rate for the rears I just pulled apart. Shocks are biltein sports (F4-B46-0179-H0). I'm planning to do the adjustable conversion to these and was planning on 180# progressive springs.

The current springs are gold in color - but no markings to indicate what spring rate. Any ideas?

TIA

Measure them. Either talk to someone with a spring tester, or just stack up weights so you can get a reasonable estimate of pounds per inch of deflection.

--DD

Just do the math or use an on-line calculator.

Formula is (11,250,000 * ("Coil Spring Wire Diameter" *4)) / (8 X "Number of Active Springs" X ("Coil Spring Diameter from the center to the center" X 3))

So you will need the following

Coil Spring Wire Diameter

Number of Active coils

Center to Center Diameter of the coil

Or just go HERE

Hope that helps

Cool, thanks Stephen.

I did not know you could calculate spring rate like that. Cool!
Zach

Well I finally had some time to play with this and it turns out the formula is wrong, but the little calculator at the bottom of the page gives the right result - 151lbs spring rate.

The problem with the formula is the way they wrote it for a browser. It should actually be: (11250000 * h) / (8 * n * k)

Where:
h = wire diameter(raised to the 4th)
k = coil mean diameter(raised to the 3rd)
n = number of active coils

In my case the number look like: (11250000 * .5^4) / (8 * 11 * 3.75^3) = 151.51

Hope this helps someone else fighting with the formula.

180 progressives the dia. of stock springs..

what progressive springs where you going to use with the adjustable spring plates ??
most are 180...