Help ID'ing 620# springs

[kslushy]

Search came back empty.

I bought a set of front springs at a swap meet on sunday, and the seller said they were 620# springs. Aside from some crude stamping numpers on the side of the springs that are only 1/2 there.. there's no markings whatsoever on them. They're brand new, and measure a little less than 13" free length from coil seat to the top end of the coil. The wire diameter on my caliper (including the paint on the spring) is ~.720". Can anyone confirm these are 620s?

Thank you in advance.

 

[red65]

k = [d^4 * G] / [8 * D^3 * N]

where:

k = spring rate (lb/in)
d = is the wire diameter (inches)
G = Shear modulus of the spring steel (11,500,000 psi is a reasonable estimate)
D = Mid-line coil diameter (this is the diameter to the center of the wire, not to the outside, in inches)
N = Number of coils

That's the textbook answer, anyway - should get you close

 

[ttoney]

k = [d^4 * G] / [8 * D^3 * N]

where:

k = spring rate (lb/in)
d = is the wire diameter (inches)
G = Shear modulus of the spring steel (11,500,000 psi is a reasonable estimate)
D = Mid-line coil diameter (this is the diameter to the center of the wire, not to the outside, in inches)
N = Number of coils

That's the textbook answer, anyway - should get you close

Now why didn't you already know that?

 

[Applejack]

I hate to break the news to you, but 620 springs don't have a spring rate of 620 lb/in, or at least the ones from Mustangs Plus don't.

Check out the bottom LH corner of page 4 of the link below (pg 192 of their '06 catalog).

http://www2.mustangsplus.com/catalog/18_suspension.pdf

 

[kslushy]

I hate to break the news to you, QUOTE]

Be happy. I was about to sell them because I wanted something in the 5xx range.

Red65: I'm aware of the calculation, but my ME roommate isn't around and the shear modulus just "seems" to me to be a bit high. Theres always an easy answer right?