CaptainSquirts wrote:I sent an email to fortune auto(coilover company) about this about a month ago and spoke about droop. I said...
"So since my rear springs are preloaded 1/8th of an inch, would it be best to try to basically have them be at 0 preload(0 meaning the spring is not compressed at all but still touching the top of the perch and the locking nut it sits on). Think the 1/8th would make a difference? Since the spring rate 11k is around low 600 pounds and my rear corner weight 650 on one corner and 680 on the other. Does that mean the springs on the rear is barely compressing thus if I go over something I won't have much droop at all?"
They replied back with..
"That's correct if you reduce the amount of preload you will increase the amount of static droop. Although it will only be a little bit but it will be some."
You really have to wrap your head around what's going on. I'm not sure they gave you a good answer. I hesitate to call it "wrong", though I sort of think that it is. But, I think it's less that they're wrong, and more that that they just aren't explaining it well.
Let's put your car on jackstands. Full droop. The coilover is just hanging there. Lower control arm or whatever is dangling from the end of it.
What happens if you adjust the lower spring perch down? Do you get more droop? If you raise the lower spring perch up and introduce preload... do you get less droop? Not really. The spring in no way LIMITS our droop. It can't. It resists compression. That's all it does.
What's determining our droop travel? What is LIMITING our droop travel? Unless you've installed some kind of a droop limiting device (like a cable, strap or chain that physically limits how far the suspension can droop), or there is some physical limitation in the suspension itself that keeps it from drooping past a certain point... the only thing left to limit DROOP travel is the shock itself. When the shock is fully extended, it can't droop any more. The spring and the spring preload is not a factor there, right?
You want more droop travel... put the car on stands, let it droop... and then adjust the shock body LENGTH. Make the shock body longer, now you have more droop travel.
And then when you set the car back down, you'll see that you've also raised the ride height, which you can bring back down by lowering the spring perch.
You'll balance those two things. The perch height and the shock length to get the travel where you want it. Maybe you want 50% compression and 50% droop? Maybe because you're stiff and low, and you have 5" of travel, you only want 2" of compression and 3" of droop. Whatever you want... you adjust those two things to get it.
Preload is kind of secondary to that. You can set everything mentioned above with NO preload. (which is how I normally do it... just enough preload to keep the spring from falling out of the perch at full droop) You can add preload from there... and it WILL raise the height of the car some. But, in addition to that... any body roll or bump that you hit will have to overcome the amount of preload before the suspension will move. I learned that you can definitely go to far with that and lose a lot of steering feel... so, preload is kind of a subtle thing that you can play with if you want to. But, up until now, I never put in more than 1/8" or so of preload... and I'm likely to continue doing it that way, at least for street cars.
So, back to the answer you got from the coilover guy, and what's "right" about what he's saying.
"That's correct if you reduce the amount of preload you will increase the amount of static droop. Although it will only be a little bit but it will be some."
If you reduce the amount of preload... you increase the amount of SPRUNG droop. Is that a better way to say it? If you drop the spring perch so far that you've got an inch of air for the spring to flop around in, you now have unsprung droop. You don't have more droop. The length of the shock is still limiting the droop, and always was. But, you're either raising the lower spring perch up into it, or you're not.
If you go the other way and add a bunch of preload. Say you add an inch of preload by raising the spring perch up. Droop is the same. But, you've actually raised the ride height a bit.
It can be hard to wrap your head around, I won't lie. But, you really need to understand "how much droop travel do I have" (from static height to wheel coming off the ground) and "how much compression travel do I have" (from static height to fully compressed bump stop... and if you're tuning bump stop and spring rates, you also want to know at what point the bump stop starts to engage).
Once you know that, you can start thinking about and playing "what if" and experimenting. If you determine that you don't have enough droop travel, then you need to lengthen the shock body and lower the spring perch. That gives you more droop... less compression.
The thing a lot of people don't realize is that you can have things set up COMPLETELY fucking wrong, and still get the ride height and "preload" that you want. Easy to do. If you go too tall with the shock body, and then lower the spring perch way down to compensate... boom, there you are. No compression travel... gonna ride like shit, and as soon as you turn the wheel, something's gonna load up on the bump stop, effective spring rate goes through the roof instantly, and you lose traction.
I think you may be in the opposite situation. You might have your shock body too short, which made you raise the spring perch too high to capture the spring and get preload. So, you probably have LOTS of compression travel, and not enough droop travel. Such is my theory... which you can quickly test with a jack and a tape measure.
. But since it has a nice chunk of extra droop it shouldn't be in a free fall state since the wheel should always be on the ground, unless like above, flew off a cliff.