suspension mystery

Shocks have more to do with supporting the weight of the car than you might think. If they were gas-pressurized shocks, the gas pressure adds to the effective spring rate. When the seals go and they lose pressure, I know on a Miata you can lose as much as 3/4" to an inch of height. On a larger, heavier car that is working with more suspension travel to begin with, it stands to reason that you could lose a lot more height than that.

This is Lemons.
All 4 of your springs have failed.

You have a 1-2" lower CG now.   You're complaining about that?    get a lower jack......;-)

Not very lemony. 
Get yerself a few chunks of 2x4 and shove em under the tires and roll forward, should get you up enough to get the jack under it (used to race an AH sprite with crap for ground clearance always worked for me)

I think you've fatigued your springs.

We cut too much off the springs on our Jag, so I use my small jack to jack up the side of the car enough to get the big jack under the crossmember.

1"-2" in one race isn't from spring fatigue.  If the bottom of the spring is on the perch you may be off at the top.  Any clanging noises as you turn the wheel?

What type of suspension is it?  The Germans are notorious for designing suspensions that have really wacky adjustments (just try doing an alignment on an early 911 with a swing-axle).  You may have something that sets ride height that has slipped.

Physics check...

When a spring fatigues due to repeated cycling from age or race use, does it lose spring rate?

No, it does not. As long as the thickness of the wire is the same and the diameter of the coils is the same, the spring rate will not change. Springs may sag, but they don't get softer.

If anything, what will happen is that since most stock springs use the spacing of the coils to provide a "progressive" spring rate, the coils that are closer together will "coil bind" and the spring rate will actually go UP. (same effect as cutting a coil)

That's not to say that you won't be bottoming out. Just saying that at no point does your spring rate decrease. Gotta love the black art of suspension tuning!

Put some SHOCKS on the car to control those springs. Just because a shock isn't completely blown out and leaking oil, or it passes the infamous "bounce test", does NOT mean that it is providing sufficient damping for good handling or enough damping to keep the suspension from bottoming out.

Actually...

I've got some very good data that shows that highly stressed (>50% UTS in this case) steel coil springs can in fact lose spring rate as a function of cycles.  No one has ever provided a good explanation for why this may occur, so I made one up: how about reduction of spring wire cross-section due to micro-cracking?  Anybody?

In addition to the obvious change-in-free-length-when-cycled thing, springs also "creep" like plastics tend to do under constant load, particularly at any sort of elevated temperature.  That means that your car can get lower just sitting there.  Lovely.

Scott

Temper of a material doesn't effect stiffness, only strength.  Stiffness is also relatively constant with respect to alloy.  Carbon steels and alloy steels have basically the same Young's moduli because they are mostly iron.  Stainless is a bit different, probably because of the large fraction of chromium.

Not really on-topic, but there you go.

Scott