NA Koni/GC install (help)

My '97 came with Koni/GC coilovers and FM top hats. I'm in the process of replacing my rear dampers and have a few questions.

1. On the damper itself, there are three slots for a ring (for placement of the spring perch). What's the correct one to choose? I'm guessing it depends somewhat on intended ride height and spring length? I was simply going to use the same one (lowest) that it was set to before.
2. What bumpstops are preferred? There were some small, foam-like ones but the passenger side disintegrated on removal.
3. Can I get replacement rubber top pieces (piece that sits above the spring)?
4. How do I assemble the strut? My problem is the top center nut. How do I get it tight, and what is the torque spec?
5. Are the used dampers worth anything or should I just chuck them? Looks like they've seen some abuse.

Thanks for the help!

Clarifications:

1. To be more precise, I'm talking about the circular groove where the threaded collar sits:

http://www.teamcotton.net/miata/DSC_0081.JPG

2. Picture of the bumpstop that didn't disintegrate:

http://www.teamcotton.net/miata/DSC_0083.JPG

3. Pictures of the rubber piece I'm talking about:

http://www.teamcotton.net/miata/DSC_0084.JPG

http://www.teamcotton.net/miata/DSC_0085.JPG

5. Used dampers:

http://www.teamcotton.net/miata/DSC_0088.JPG

OK... I'm still trying to figure all this out. I've only done dampers once a while back on a car without as much support/info as the Miata so I'm a bit lost in the sea of info available.

At this point I'm looking at FCM bumpstops. According to http://forum.miata.net/vb/showpost.p...01&postcount=1 I should use a 36mm FCM and trim to about 20mm for the rear with a 9mm spacer.

Trying to figure out what else I need. The instructions for the FM top hats mention a pair of collars for each damper (step 10) that I don't have: http://www.flyinmiata.com/support/in...ock_Mounts.pdf
"10) Included with each new shock mount is a pair of collars to locate the shock shaft in the spherical bearing. Press both of these collars, one from the top and one from the bottom, into the spherical
bearing. These collars are not required for shocks with a 5/8” shaft such as Advance Design."
What are they and do I need them?

Also, I'll be getting new spring isolators from FCM. They talk about using stamped washers with them. Do I need the stamped washers and the upper/lower bushings since I'm using FM top hats?

Good stuff on bumpstops here -> http://www.dfwmiata.com/threads/1715...ight=bumpstops

I got my bumpstops from RE Suspension since they were TCB approved. ;-)

I don't know anything about the FM Top Hats so can't really help ya with them....

Quote:

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Originally Posted by POS Racing

Good stuff on bumpstops here -> http://www.dfwmiata.com/threads/1715...ight=bumpstops

I got my bumpstops from RE Suspension since they were TCB approved. ;-)

I don't know anything about the FM Top Hats so can't really help ya with them....

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Thanks. I had read through some of that thread in research earlier today but finished the whole thing now along with the grassrootsmotorsports post. Good info. I am, however, confused about the fender washer discussion. The NA shock assembly looks quite different from the NB. Mine looks more like the NA assembly but is missing the nylon isolator (presumably because I'm using FM hats?) and the boot and bumpstop (single unit?). It also has a GC spring isolator that sits between the top of the spring and the hat. And I don't know what that foam-like piece is that disintegrated on one side. Also, TCB?

I guess I got in over my head on this one. It happens often...

Why not set them up the way FM did??

http://www.flyinmiata.com/index.php?...7100%20%2010MM

Quote:

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Originally Posted by POS Racing

Why not set them up the way FM did??

http://www.flyinmiata.com/index.php?...7100%20%2010MM

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That's why I was looking at the FM instructions (and step 10 mentioned before), but they don't specifically talk about Koni or GC (or coilovers period).

Yep they don't mention them since they are assuming you bought them new to fit the Koni's.

Quote:

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Available to fit all Miata shocks other than the AFCOs. Please specify shaft size when ordering. If your shock is not on this list, please check the diameter of the shaft. If you did not have to drill out the hole in your stock perches, it`s 10 mm.
10 mm: fits KYB AGX, KYB GR2, Tokico Illumina, Koni STR-T (orange), Tokico HP and stock shocks.
12 mm: fits Koni Sport (yellow) shocks.

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Didn't these have Koni's on them already?? So they should already be set up for use on a Koni with a 12mm shaft size right??

Quote:

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10) Included with each new shock mount is a pair of collars to locate the shock shaft in the spherical
bearing. Press both of these collars, one from the top and one from the bottom, into the spherical
bearing. These collars are not required for shocks with a 5/8” shaft such as Advance Design.

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Quote:

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Originally Posted by POS Racing

Yep they don't mention them since they are assuming you bought them new to fit the Koni's whick is one of the options.

Didn't these have Koni's on them already?? So they should already be set up for use on a Koni with a 12mm shaft size right??

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Right. The top hats fit the Konis fine. It's the other pieces of the puzzle I don't have figured out. Bump stops/spacers/washers/bushings/isolators/collars. The FM instructions don't mention coilovers and when you're using stock or lowering springs it's a more defined/standard setup I guess.

So, I noticed this while removing/disassembling but I didn't consider the implications until today. The springs I have (7" I think) are short enough such that they don't require compression for installation/removal on the shock assembly. This means that when the suspension is, for the most part, under no compression (weight) the spring is free to move about which means it's possible for it to shift then on compression, land off center of the upper mount. This sounds less than ideal, if not dangerous/destructive. Or am I just crazy and don't know what I'm talking about (very possible!)?

^Is that only when they are un-sprung, or even with the car/tire on the ground?

Quote:

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Originally Posted by sammm

^Is that only when they are un-sprung, or even with the car/tire on the ground?

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I think it's only when unsprung, but I didn't think to look that closely when the car was on the ground. If it is only when unsprung it probably isn't that big a deal. It's not like I'm gonna rally it with this suspension... But I do have to make sure the springs are centered on the upper mount when I put the car back on the ground after installation.

Edit: I assume just about any weight at all would be enough to keep the spring in place on the mount, even if it doesn't compress it much. Plus, with relatively stiff setting on the damper, it should be unlikely to extend to the point where the spring is completely uncompressed.

Also, is there a possibility for the inside rear corner to become unloaded enough to cause this to be a problem?

Here is a picture of what I'm talking about:

http://teamcotton.net/miata/2013-03-01_11-20-20_150.jpg

How worried should I be about this?

Shouldn't I be able to raise the perch up to meet the upper mount without affecting ride height since the spring location is what affects that and not the shock? The shock is just going to come down to rest on the spring anyway.

Quote:

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Originally Posted by GroceryHauler

Also, is there a possibility for the inside rear corner to become unloaded enough to cause this to be a problem?

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Yes there is a possibility. Couple of examples hit a dip take a corner quick any of these maneuvers can cause the shock to become unloaded.

Why not add a little preload just to make sure the spring stays in the pocket of the shock mount? Or are you going for Hella Flush look where you want it as low as she will go??

Quote:

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Originally Posted by GroceryHauler

Here is a picture of what I'm talking about:

How worried should I be about this?

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I would be....can't you raise the lower perch?

And another vid!

Quote:

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Originally Posted by sammm

I would be....can't you raise the lower perch?

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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.

Quote:

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Originally Posted by 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.

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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??

Quote:

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Originally Posted by GroceryHauler

Past that point will increase ride height.

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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?!?! ;)

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.

Quote:

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Originally Posted by POS Racing

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??

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

Quote:

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Originally Posted by sammm

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?!?! ;)

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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.

Quote:

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Originally Posted by 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.

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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?

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.

Quote:

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Originally Posted by 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.

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

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.

Quote:

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Originally Posted by 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.

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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?

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

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?

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??

Quote:

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Originally Posted by 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??

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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...

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?

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

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.