NA Koni/GC install (help)

[sammm]

Past that point will increase ride height.

I've never messed with coil overs, but adjusting the perch doesn't change the overall length of the shock, does it? It could raise the height, but will also increase rebound (I think). Where's the pointy head types when you need them?!?!

[OZMDD]

You should preload the spring, meaning raise the perch to prevent it from moving in full droop. This is the purpose of tender springs. You can change ride height somewhat this way, but you typically are limited by the length/travel of the spring. Some coilovers have two adjustable areas; one for preload (spring length) and one for perch location relative to the car (ride height). To my eye, your setup looks like it has limited height adjustment based on spring length and travel. I might be mistaken, but I'd assume that is the whole reason fo the FM tophats, so that the car can be lowered without losing all shock travel.

[GroceryHauler]

Where you have the perch set I'm thinking the cross member might touch the ground.

Have you put this setup in the car and put the car on the ground to see where you are at now??

No, but I don't think that's happening because essentially, this is how it was set up before I removed it.

I've never messed with coil overs, but adjusting the perch doesn't change the overall length of the shock, does it? It could raise the height, but will also increase rebound (I think). Where's the pointy head types when you need them?!?!

This is my first set of coil-overs which is why I'm trying to get clarification on everything. The perch definitely does not change the shock at all. It merely changes the relative position of the spring. I don't know if/how it would increase rebound.

You should preload the spring, meaning raise the perch to prevent it from moving in full droop. This is the purpose of tender springs. You can change ride height somewhat this way, but you typically are limited by the length/travel of the spring. Some coilovers have two adjustable areas; one for preload (spring length) and one for perch location relative to the car (ride height). To my eye, your setup looks like it has limited height adjustment based on spring length and travel. I might be mistaken, but I'd assume that is the whole reason fo the FM tophats, so that the car can be lowered without losing all shock travel.

That is my thought at this point, although I don't fully understand preload. I want to preload it some so the spring isn't free but that does significantly limit ride height adjustability. How much can/should I preload the spring? The more I preload it, the higher the ride height will be, correct?

Also, what are the rent-a-spring-compressor from autozone or o'reilly rated for? Will they handle these 400# springs?

[OZMDD]

You don't need spring compressors for coilovers, since you can just back down the spring perch. Also, they have less travel. Preload essentially accounts for the weight of the car on that corner, so that the unloaded "droop" doesnt unseat the spring. It doesnt need to be all that much for basic setup. You could set it by adjusting the perch with the suspension unloaded and raising the perch until the spring is snug to the upper perch. Not exactly mathematically precise, but will do the trick for keeping the spring on the perch.

[GroceryHauler]

You don't need spring compressors for coilovers, since you can just back down the spring perch. Also, they have less travel. Preload essentially accounts for the weight of the car on that corner, so that the unloaded "droop" doesnt unseat the spring. It doesnt need to be all that much for basic setup. You could set it by adjusting the perch with the suspension unloaded and raising the perch until the spring is snug to the upper perch. Not exactly mathematically precise, but will do the trick for keeping the spring on the perch.

I think I follow. But then how do I make adjustments to ride height, if necessary?

[OZMDD]

That's where I'm less clear, since mine are multi-adjustable. From what I'd gather, you can only raise ride height, not lower it with your coilovers, unless you eliminate your droop travel. Also, you can only raise it to a point, as you will eventually reach the limit of shock travel. Beyond that range, you'd need different length shocks or springs.

Since your setup is VERY widely used, I'm guessing it provides a desirable ride height as-is, unless you are using different length springs than others do, or your setup was intended to run tenders.

[GroceryHauler]

That's what I mean. I should be able to raise the perch without affecting the height. Up to the point where the top of the spring meets the bottom of the upper mount. Past that point will increase ride height.

I take it back. The important parts that determine ride height (now that I'm thinking about it) are the spring length and the relative position of the spring perch to the lower shock mounting point (lower control arm). And technically the upper mount (especially given these FM mounts)...so basically:

1. Spring length
2. Spring perch position relative to shock mount point
3. Relative position of the top of the spring to the chassis.

Something relating to the lower control arm probably could affect it to, but I'm stock there so I won't worry about that for now.


So, raising the perch will raise the ride height. I'm too low as it is and planned on raising ride height anyway but it sounds like it might be a challenge to get the perfect ride height with enough preload to keep the spring in place. I probably need to look up a good procedure for adjusting ride height on these (or similar) coilovers. OZMDD, are you saying I can load the spring simply by raising the spring perch? It wouldn't "unscrew" under the pressure of the spring?

[OZMDD]

Most have two rings so they can tighten against each other to lock, or a set screw.

[GroceryHauler]

After some more research, it sounds like helper springs are the appropriate solution here. I didn't know the difference between tender and helper springs. Still don't know how preloading fits into it all. Any idea if/where I can get 2.5" ID helper springs along with the appropriate spacer locally tomorrow?

[POS Racing]

If you add helper/tender springs you are going to raise the height of the entire assembly aren't you?

Also you had this exact setup under the car prior to taking everything apart?? So what has changed that has the spring so loose??

[GroceryHauler]

If you add helper/tender springs you are going to raise the height of the entire assembly aren't you?

Also you had this exact setup under the car prior to taking everything apart?? So what has changed that has the spring so loose??

As I understand it the helper spring is just going to keep the main spring in place even at its current position. The helper spring is very low spring rate and will completely compress (bind) under the static weight of the car. That said, it will raise the height by as much as the thickness of it at full bind (3/4" ish I think).

Nothing changed apart from replacing the damper. That's what's scary. As soon as I jacked the car up, the spring was loose. I just didn't realize the implications of that until now...

[GroceryHauler]

Since I couldn't convince any of my friends to help me today, I didn't get very far. But, even with help it feels like getting that top nut on the shock assembly torqued will be pretty tough. I was hardly able to get any torque on it at all before the shaft starts spinning.

Now that my progress for the rest of the weekend is shot, I can think about getting helper or tender springs for next weekend. Going with helper springs will be more straightforward. Two questions I have about tender springs:

1. It seems like you have to get the spring rate and length just right for a particular application (vehicle weight and compression damping). Is that true and if so, what's the downside of not getting it right?
2. Is it a good idea to have a dual rate setup in the rear but not the front?

[POS Racing]

Have you asked the questions on Miata.net lot bigger audience that this place. May be someone there that has first hand experience with what you are trying to do.

http://forum.miata.net/vb/index.php

[GroceryHauler]

Decided the dual rate setup wasn't worth the trouble. Probably should have gone with helper springs but didn't in the end. I'm not too worried about unseating the spring, but I'll keep an eye (and ear) out.

Almost ready for some more autocrossing. I had my end-links adjusted and they started clanking so I disconnected the rear and now no noise. After firming up the rear shocks I think it actually feels better (even when the bar was set to the softest setting). I don't actually know what bar it is. Maybe someone could identify it at the next Wednesday JJ GTG.