spdracerut

Fatigue life needs to be taken into consideration also. Though a material is not taken to its yield point does not mean that it is not being fatigued and weakened. Back to my initial thought on annealing. If the spring was cold formed, there may be residue internal stress that is relieved with moderate heat application. Maybe even if the spring were formed hot, there may be some residue internal stresses after air quenching. That's the best I can figure.

Back to fatigue life. Car chassis get fatigued after time and less stiff. Military aircraft, especially fighter aircraft have fatigue life limits. The frames aren't stressed to yield, but repeated stress application causes them to get softer over time. I was doing my senior project with Lockheed and had some pretty interesting conversations with the engineers there. He said you could tell when a pilot had really beat on the plane by pulling lots of high G turns as sometimes the airframes would be junk afterwards. Also, the planes gain weight over time as they are repainted often. Just another tidbit I found interesting.

dan_uk

I preloaded the bushings and drove it around a week before the CB and its dropped over 1/4" somethings given way

thanasis11

Fatigue life goes back to manufacturing and quality. A spring that will fatigue after a few hundred thousand cycles (a few days of driving) was not manufactured properly. On the other hand I can understand my springs sagging after several years of use because of fatigue.

spdracerut

So I guess we can come to a conclusion that some springs will 'settle' more than others due to different manufacturing processes and material quality. Now only if that information were easy to come by for each manufacturer of springs

thanasis11

well a properly made spring should not sag/settle at all especially when its new. now go put 70,000 miles on it and it might start sagging. with 500 miles the difference will be immeasurable.

thanasis11

http://www.eatonspri...ingsettling.htm

this is the most credible link I could find regarding our conversation guys straight from Eaton, a spring manufacturer, they make leaf springs rather than coil springs but the concept is exactly the same. This basically reiterates what I have been saying.

Hoang

Stock don't need to be aligned as it was machine built to a required specification but it will slightly settle as the vehicles shipped to the dealer all contain a rubber piece holding in between each rings of the springs. Thanasis, if you don't believe it "needs" time to settle (not sag nor fatigue life), drive it 2 more weeks - 1 month and you shall see. You already did an alignment on your brand new hand swapped suspension which clearly already prove that you don't believe in this matter. This is not a complex question for you to go into detail with engineering mind set and science to prove a fact. My PSS9 did, just as other coilovers I have helped install from BC, Megan, KW to Teins.

thanasis11

So you are saying that the Teins will sag because they are not machine built to a require specification? What about valve springs? Do my valves sit lower after 500 miles of changing valve springs?

spdracerut

Not sure valve springs are a good analogy. No one is going to complain if the valve springs are initally overly stiff and then soften up to specification for creating the proper seat pressure.

At the end of the day, we as end users have no control over how the springs are manufactured or to what specifications. The best we can do is to determine which spring companies do produce the best springs according to our metrics or values we set on parameters we determine important. From what many of us have seen from experience, many if not most springs have an initial settling period.

thanasis11

im done with this argument. let your springs sag. in the universe that i live in they dont thank god.