B serious

The distance from the tophat to the spring, is volatile.

It moves with the suspension.

This is the exact thing you were planning on doing before....there's no difference.

You shouldn't do that.

As described, the swaybar and bushings will cause bind and you will never get a good "zero"

Its not a reliable or viable option.

You need to ensure that the shock is fully extended when you set preload originally. You can't ensure that if the shock is installed in the chassis.

You need to either remove the shock or put the suspension into FULL droop so that the shock can extend without resistance from other suspension components.

MauiMana

Based on the discussion about the bushings and sway bar spring compression, let me back up a bit to make sure I am actually making the correct assumptions about my preload being off. I determined there there was a difference in preload from what I observed when I was raising the front ride height a bit. Doing one side at a time I saw that the driver's side had about 1/2" more distance between the bottom bracket (nut) and the spring perch than the passenger's side. And of course prior to jacking up the car I had verified that the overall front ride height was even on both sides. So was I correct in interpreting this difference as being a difference in the preload?

B serious

Lol you really don't want to remove the suspension, eh?

It means one side has a different adjustment than the other. Could be length. Could be preload. Could be unevenly clocked bushings. Could be some damage in the suspension. The only way to know is to initialize the suspension by removing it off the car and setting it properly in the first place.

Here's the easy way:
Does the car ride ok? Any issues?

If not, then maybe just leave it alone. Who cares if the adjustment is off as long as your ride height is even and you feel it rides/drives fine.

I wouldn't try and do what you're thinking about doing. You're probably better off just leave it alone if you don't want to do it correctly. You need to have the initial number before you start adjusting.

If its enhancement or optimization you're looking for then uninstall the shocks. Start your adjustments from scratch. You're selling yourself short by trying to take shortcuts.

No offense, but you're asking the same questions and expecting the answer to change so that you feel better about doing it the wrong way. But you don't need anyone's permission to do what you want with your car. My recommendations are listed above a bunch of times.

Car Analogy

I think you may be misunderstanding the impact of preload. Maybe you're thinking one side is stiffer than the other due to preload mismatch. That is not the case.

Add 100 lbs to either side, and that side will compress tbe same amount. You jave same spring stiffness on both sides even if preload differs.

The reason is that even though spring is preloaded on the bench, its not on the car. On the car the preload only sets the shocks ratio of droop vs compression.

A thought experiment. Imagine the car sitting on its suspension. Now you magically raise the lower spring perch. You add preload. What happens? Does the spring compress more than before? No. The car simply rises (on the bench the spring would compress more because there is no car sitting on it. That is why they call it preload. But personally I think the term causes lots of misperceptions).

If you were really adding preload, you'd next return the car to desired ride height by adjusting the shock length.

Can you see now the purpose of preload? Its to set the at rest ratio between how much travel the shock has going down, vs how much travel going up. Droop vs compression.

So if your preload is really off one side to the other, the car will ride and perform exactly the same on both sides, up until you reach the limit of travel. One side will hit the bump stop before the other.

That could be an issue in the rear for our cars, since travel is limited there. You coukd easily end up riding bump stop at rest in the rear on one side. But the fronts not so much.

This is why B is saying maybe doing worry about it so much. Its the front, and it doesn't change how suspension performs until you hit bump or droop stops.