Suspension Spring Stiffness Rates

[jmettee]

Anyone have the spring stiffness rates of the various units out there?

Fronts
Stock: ?
Eibach: ?
Grady: ?
Martins: ?
Other: ???

Rears
Stock: ?
Eibach: ?
Other: ???
It would be good to know how the rates compare to be able to decide what to go with, & how they all compare.

[content22207]

Measure new units -- springs lose elasticity every single time they are compressed.

Bill Robertson
#5939

[Nicholas R]

Really unless you actually yield the metal or excessively heat or cool them, they shouldn't ever change though. That's the point of a spring after all.

Also to answer your question, in Ohio we did some extensive testing on lots of springs old/new, front/back from many different vendors, including springs with hundreds of thousands of miles on them. They were all almost identical. I THINK (i'll double check the data) that they were all almost exactly 150 lb/inch. It was very surprisingly consistent.

[content22207]

Suspensions sag with age. Valve springs eventually wear out. Throttle return springs need to be replaced. Etc. Springs are more elastic than ordinary steel, but every single time you compress/tension one it does lose a minute amount of its springiness.

Springs wear out in ammunition clips.

I even had to replace the spring on my back storm door once.

Bill Robertson
#5939

[dvonk]

mmm, the Second Law of Thermodynamics in action!

[content22207]

https://www.youtube.com/watch?v=6QaT6o8fJ1Q

Bill Robertson
#5939

[DeLorean]

How fast a spring "wears out" depends entirely on it's initial quality and the sort of load it's under.

A typical automotive grade spring is going to have almost 100% of it's original "springyness" if it's properly designed 200K miles down the road. Most cars, you NEVER have to touch the springs.

An interesting counter example? Saab 9-3's never have sag or handling issues, and the springs never "look" bad. They will however frequently crack right near the spring perch and occasionally take out the tire when the spring goes. You can not tell visually when this is about to happen in any way.

[DCUK Martin]

springs lose elasticity every single time they are compressed.



This is complete and utter rubbish. "losing elasticity" doesn't even make sense.

What you're talking about is creep, not yield, that has an effect over a very, very, very long time (eg 30 years for a door torsion bar to need tightening by 1 notch). A spring should never experience fatigue either.


How fast a spring "wears out" depends entirely on it's initial quality and the sort of load it's under.

I would say it has everything to do with quality of manufacture - if properly designed, a spring should never be pushed/pulled anywhere near the yield strength of its material. Poor quality materials may experience fatigue, accellerate the effects of creep and/or cause the initiation of cracks as the surface corrodes.

FWIW mine are made from high quality chrome-silicon steel. I don't actually know the rate, but I can find out.