lobuxracer

iTrader: (2)

In simple terms: the shorter the spring is the more compressed it is, the higher the car is. The longer the spring is the less compressed it is, the lower the car is.

This also touches on something important in bike set up that car guys don't seem to do. Preload (the amount the spring is compressed at neutral height) and ride height are independently adjustable on bikes. Cars seem to just alter preload to set ride height (with the exception of a few shocks I have seen that do allow ride height and preload to be independently adjusted.) I've never quite understood why cars don't do this. The obvious exception is pushrod suspensions like champ/irl/formula cars have where everything is independently adjustable.

Gernby

iTrader: (1)

The JIC FLT-A2's allow separate pre-load and height adjustments. I had to preload the hell out of them on my S2000 to prevent the dampers from bottoming out on big bumps.

lobuxracer

iTrader: (2)

That's a long and difficult discussion. The rule of thumb for preload on bikes is the suspension should be 1/3 compressed at neutral. This is part of why I don't understand using preload for ride height. Adding preload shortens the amount of travel available to top out and increases the amount of travel for compression, which isn't always a good thing at all. If you are dropping the car by reducing the preload, then you get less compression and more top out. Which also doesn't make sense from a ride tuning perspective.

I'd much rather pick a spring rate and preload to give me about 1/3 travel at neutral, and adjust ride height until the car just barely scrapes on the worst parts of the track (or in the case of street driving, the worst bumps I normally encounter). Then I can look at roll center and roll axis to see if I'm where I want to be...

nabisco

Thanks a lot guys! I was lengthening them at first and then two of my friends told me to go the other way. Now I get to make them do the right adjustments! My hands are killing me!

cspec

Also, how do you know they've been tightened enough? I wouldn't want them to be too loose... Or should I just tighten them with all my strength?

Gernby

iTrader: (1)

What are you talking about? There isn't anything that should be tightented "with all your strength". If you are talking about the locking rings on the spring perches, it would be dangerous to over tighten them.

Gernby

iTrader: (1)

You ain't kidding about the long discussion. It got REALLY long and complicated when I posted about the issue with my JICs. Basically, if they weren't preloaded (like JIC required), and you lowered the car only 1", the dampers were about 75% compressed at rest. I had to void my warranty (according to JIC) by preloading my springs about 3/4" to acheive a 50% damper compression at rest with a 1" drop.

cspec

Whoops, sorry for being so unclear, yeah the spring perches... How do you know it's tight enough?

Gernby

iTrader: (1)

The lock rings just need to be slightly tight. If they aren't tight enough, then they will just allow the perches to slowly fall (VERY slowly). There is no danger in them being too loose. It isn't like loosing a lug nut.

lobuxracer

iTrader: (2)

That's an interesting thread. All the basic texts on chassis setup tell you how to calculate wheel rate from taking a few measurements on the chassis and knowing what your spring rate is. Wheel rate is what one of your guys was guessing at but assumed the spring rate and wheel rate were the same (they are not unless the shock is mounted vertically at the ball joint, and it never is.)

I am stunned the importer knows so little about setting up adjustable shocks. Kind of scary if you ask me.