coilovers advice

[NoHachi]

40kg/cm = 40N/mm or 4kg/mm just in case. Even that is highish..

[Uzelac]

Well.. ~20kg is stock AFAIR.
30-40kg would be great for daily, but who really use AE86 for daily ?
Daily with coilovers and very low ride height ?

I stay with 40-60kg/cm

[robotype]

OK I did about 100 kms yesterday and as expected the verdict is definitely too harsh. Not usable on public roads (at least italian roads...). Maybe I can get used to it but the passengers won't be happy expecially my wife. We still have stone roads in milano!!

I need to replace the springs asap. I think the biggest problem are those cut springs in the back, no clue about the rate but they are too low and too hard. by the way the car is not even...the guy at the shops really needs a new pair of glasses.

So I was thinking 40kg rear and 60 front, could it be a good compromise? what about height and diameter for front and rear?

[NoHachi]

Still too high.. to be useable on the street think more like 4kg/mm front maximum. I have 6/4.5 on my trackday car and its harsh everywhere else. Its also borderline compared to the chassis.

I still think the ideal street setup is escort mk2 GP4 tarmac spec.

[robotype]

so 4kg/mm front and rear? what about the measurements of the springs, are they all the same lenght/diameter?

the swift 080 I have now looks very short, would a longer spring help or is it just a matter of kg/mm?

[NoHachi]

First off, you would do yourself a big favour by reading up on this subject and how everything interacts. It will make it a lot easier for you to figure out what suits you and how to get to that.

Springs, if you chose 4kg/mm fronts, look for something around 3kg/mm rears.

Spring length, visualise this: when the car is in the air (jump or similar), the shock is fully extended. This position is the first datapoint. If your spring free length is shorter then this length then the spring can rattle and unseat. Your secondary spring on the front is a very weak spring that is normally fully compressed, but in this situation opens and keeps everything in place. Its springrate is matched to the weight of the wheel, not the car. So that it can control tire movement when there is no weight resting on it. This is a good thing.

Now, imagine a very weak and a very stiff spring. Put a weight of 250kg = 300kg on both of them (weight of quarter of the car). The stiffer spring will move A LOT less. Since both of them need to support the same weight, the stiffer spring will be shorter then the weak one ( which NEEDs to be longer).

You can calculate the length of the spring you need by using the calc on page 47 here:
http://performance-suspension.eibach.com...-17_US.pdf

[robotype]

thank you what you explained is quite clear for me. what I wanted to understand is this: there are two springs with the exact same stiffness, the only difference between the two is one is twice as long as the other. now, if I use the first on the right wheel and the other on the left...will they behave the same? I don't think so...in my immagination the longer spring will drop more than the short one because with the same weigth if the short one shrinks 1 cm the long one will shrink 2 cm...

anyway long story short, if I want 4kg springs for the front I should not worry about the lenght because if it's 4kg that's all I want to know. then I can adjust it with the nut rings on the strut thread. correct?

[NoHachi]

No x kg/mm is x kg/mm, that means that a spring will move 1 mm for each x kg. Spring length is not of influence on spring [u:3abeff90fe]rate[/u:3abeff90fe].

Your feeling comes from the fact that softer springs NEED to be longer because they are softer. If you have a 200kg on a 10kg/mm spring it will move 20mm.
If you put the same weight on a 2kg/mm spring, it will drop 100mm. Its easy to imagine that the 10kg/mm can be shorter, say 60mm, and work OK. But 60mm on the other spring would be way too short, it moves more then that due too the weight, so it will collapse to its block height (all windings stacked).

So spring length is important! Read the link I sent!! Do your own thinking.
In general you want:

That the spring is long enough to absorb all the weight it will see (roughly cornerweight + dynamic load = 2x cornerweight roughly) without coming close to block height.

That the spring is short enough that it moves the spring more then 10% with just the weight of the car on it.

If you don't have helpersprings then you also get the extra problem that the spring length needs to be at least equal to the shock stroke.

After you figure this out, you buy the spring and set rideheight with the collar.

[Spitfire]

I'm using a longstroke setup with 5.2 kg/mm and yellow Koni's at the front and its way too stiff on broken roads. I had 3.8's before and it was a lot more comfortable and still extremely fun to drive.

Some hate everything above 3kg's, some love to skid around and dont want to go lower then 8kg's. Its all about what you want from your car.

Just my 2¢...

[robotype]

I am getting used with my 8kg (not my wife), it's like driving a gokart!

if only italian roads were a little smoother