Spring Tension

[Longfellow]

I recently discovered my front springs (KTS Coilovers) where able to be easily spun by hand when the car is suspended off the ground. There was no abundant free play but just enough slack for them to be able to be rotated with little force. I tightent them up just enough so it now requires quite a bit more force to rotate the spring and it feels a bit skittery now driving around. What do you suggest for tuning spring tension? Its mostly used for daily/spirited driving.

I think im going to loosen them back up some because they have to much preload.

[Def]

Preloading your springs is stupid and I have no idea why it's "what you do."

Any preload you put on the spring reduces your droop travel on that corner, and that's one of the main things our cars need to actually have the suspension work.


Loosen them up to where the spring is just barely held in the perch with the car up at the most.

[a_ahmed]

Get helper springs?

[jmauld]

Helper springs are a waste, IMO. They are just unnecessary weight.

Tender springs could potentially help with the droop problem that Def is referencing.

Here ya go:

Eibach has developed the ERS Double - Spring System that relies on a Main and Tender spring concept that provides a softer initial rate when both springs are compressed together, then delivers the desired firmer ending rate once the Tender spring closes completely. The Main spring has a linear-rate characteristic and determines the final rate of the system. The Tender springs are available in a variety of linear-rate as well as progressive-rate characteristics and determine the initial rate of the system.

A Helper spring is used to prevent the Main spring from becoming loose in the spring seat when the wheel is at full droop. The Helper spring, unlike the Tender spring, has very little spring rate, and therefore has no effect on the suspension characteristics of the vehicle. Up to 50mm of spring-to-perch gap can be covered with the use of a Helper spring.

A coupling Spacer is used to connect Main and Tender springs. Eibach offers both inside and outside diameter coupling Spacers depending upon the dimension and function of the specific damper utilized.

Eibach ERS Springs can be used with or without Tender or Helper springs.

From my previous calculations, most of the available tender springs are still going to fully compress with the typical corner weights that we have. They will only come into play when unloading weight off of one corner. IE, the inside rear tire during a hard turn.

[Def]

Yes, you want tender springs. I've got some 2" free length 50 lb/in H&Rs I'm going to test in the rear. They seem pretty soft, so I'll see how much of a difference they make. Travel to coilbind is only 1" or so, I was hoping for more. But 1" is over half of what the main spring gives with my rear corner weights and spring rates.

[a_ahmed]

Hmm I thought helper and tender springs were synonymous for each other. I guess I just didn't know.

What I do know is Sasha showed me some 0 rate helper spring with some plastic spacer from Eibach and he said it was useless as what would happen is it would get stuck on the spacer LOL... and not do anything in turn...

So then.. these tender springs are the answer... I need them too, especially when I lower the car... I just wasn't sure what length and what rate to go for... front and rear...

He is getting some for himself but not sure what yet. Will give me part numbers. He told me also eibach doesn't have much of a selection of helper springs (dunno if he meant tender springs too) but hyperco does...

I like when I don't know stuff and you guys correct me, always something to learn

[Def]

Hypercoil only has helper springs - they don't affect the suspension at all when you're driving.

Eibach has a ton of different lengths and rates of tender springs. H&R has 50 lb/in in two lengths and 2.5" ID. They have more rates and lengths in 60 mm ID.

You can calculate the overall spring rate for a two spring system with one not in coilbind with this equation:

1/overall spring rate = 1/main rate + 1/tender rate

[Epstein]

A 50lb spring sounds like a good choice. It's very much less than the main springs that we're running, so it'll probably be bound most of the time. But it's stiff enough to force the wheel down where it would just be hanging there unsprung otherwise.

Ahh, the parallel resistor equation. That means you can also do:
(main*tender) / (main + tender) = combined rate.

[jmauld]

Is ~40lbs enough to push the shocks down when you get into a droop situation? I was thinking the 200lb spring was going to be required to push the shock down quick enough? I honestly don't know how to determine this though without trial and error, and those little springs are kind of pricey for that.

[Def]

It doesn't take too much to extend the shock, but a 50 lb/in spring is as light as I'd go. I was wanting to go more in the 125-175 lb/in range, to give an overall rate with my 380's to be somewhere around stock when the tender spring came into play but I got a reasonable deal on these 50s so I went with those for the time being.

Might move them up front and go with some 60mm ~150 lb/in tenders if I think those will work better, but I think these will help alleviate a lot of the wheel lift on street driving and occasional track situations(curb hopping etc.).

[a_ahmed]

A 50lb spring sounds like a good choice. It's very much less than the main springs that we're running, so it'll probably be bound most of the time. But it's stiff enough to force the wheel down where it would just be hanging there unsprung otherwise.

Ahh, the parallel resistor equation. That means you can also do:
(main*tender) / (main + tender) = combined rate.

Mind explaining that equation a bit?

It doesn't account for lengths either?

If I were to then use my 600lbs/inch spring + say a 50lbs/inch tender spring, then...

(600*50)/(600+50)=54.54~ eh?

[Def]

Lengths don't matter.

I don't know if you did the calculations right, because the rate will ALWAYS be lower than the lowest rate when both springs are in play.

I get 46 lb/in for a 600/50 combo. But that's the spring rate ONLY when the tender isn't blocked. For a 2" H&R spring it only has 1" of travel, so once you get 50 lb on that corner it is blocked and your spring rate is 600 lb/in.

[a_ahmed]

30000/650=46.15~ oops i dunno how i got 54.54 eh gay.

Okay so now that we got that right lol.

What is this calculation for then? It's not the overall combined rate ? Rather it's the rate at which the tender springs works? Until its compressed completely then the 600lbs/inch spring takes over?

[jmauld]

It's the combined rate UNTIL the tender springs compresses completely. At that point you go back to the rate of your primary spring.

[a_ahmed]

Ah that makes sense, cool