TypeFD

iTrader: (1)

Hey there everyone, have an issue with my 93FD (75k miles) bottoming out.

SETUP:
Koni Yellow shocks
Eibach springs
Ground Control C/O's
Tire Pressure: Front 30psi, Rear 28psi (cold)
Tires: 225/45 17 (17" TSW wheels)
Height: 25" Front, 25.25" Rear (measured from ground to fender lip)

BACKGROUND:
All this came from Nick at N-tech and spent about 25k miles on my previous FD, which was then grounded for over 5 years due to blown motor and career getting in the way. So these things have about 25k miles on them and at this point about 6 years old. As luck had it, I was able to pick up a mint condition FD last year, and decided to use my previous one as a donor/parts car. The entire setup came out of the previous FD (which had none of these issues) and went into the one I recently obtained. Issues manifested right away.

SYMPTOMS:
The rear would bottom out from deep dip in the road or driveway. It is most profound when pulling out onto the street from a driveway or a parking lot (not necessarily steep). The front would pull out just find but the rear would dip and bottom out on what feels like a chassis (as if springs lost their compression ratios). If I pull out veeeery slowly then the problem does not occur.

Coincidentally, I also get a clunking sound coming from the rear suspension underneath the car. Based on my research, it seems pillow ball bushings would be the culprit. The clunking started happening only recently however, almost 5k miles after the new suspension setup was installed and driven. I'm ok for now on troubleshooting the clunking.

I am concerned about the rear bottoming out. It doesn't really do that going over bumps/pot holes but if there are bumps and a dip in the road... wholly *****... feels like my **** just fell out.

Requesting assistance as anything I was able to find on the forum/archives did not indicate a clear resolution of this issue. Many thanks.

Mahjik

iTrader: (1)

Have you tried adjusting the Koni's to see if the dampening is still working (i.e. try increasing the the stiffness)?

Also, do you know what perch the rear springs are mounted on?

TypeFD

iTrader: (1)

Mahjik... we meet again... Thanks for the reply.

I tried playing with the stiffness rates on the shocks - working as it should be. Also, before I put them in I checked out the play, they compressed and released as they should. Nothing unusual was observed.

The rear springs are mounted on the top perch (I got more c-clips from Koni and installed them on the bottom two perches just in case - I had an incident long time ago .

TypeFD

iTrader: (1)

Ok, so this has been getting so damn annoying that I decided to go back and find out exactly what's going on. I tried looking for 2 hours on this forum in attempt to find comprehensive writeup of the koni/eibach/gc install and found none. There is some info on koni yellows replacements, but not very clear.

https://www.rx7club.com/showthread.p...ellows+install

I've narrowed down my woes to a "mounting rubber" that sits normally on the OEM "Bound stopper assembly."

In the aforementioned discussion (link), the "mounting rubber" is opened up (drilling) and mounted on shaft, resting on the welded part. It is then secured with a collar and a nut.

Question: is this all done underneath the shock column before chassis is lowered and rested on shock/spring? Or does the nut get tightened down after the chassis is rested on the shock column and tightened from a top of the engine bay?

My understanding is that it's a shock, "mounting rubber", then collar, chassis, "stopper rubber", then nut?

Thoughts anyone?

P.S. You can identify exactly what "mounting rubber" and "stopper rubber" are in shop manual section R.

Eggie

Just checking here... The ride heights were measured on the new chassis, right? What spring rates & lengths do you have?

TypeFD

iTrader: (1)

Ok, may be this will help. What we have here is a Koni Shock, Ground Control Adj. Coilover, and an Eibach spring.

At the bottom of the picture you will notice a mounting rubber, that has a collar in it (visible) and a metal washer resting brake dust cover. These three are supposed to mount on that perch on at the top of the shock rod underneath the column???

I'v been driving the car without the "mounting rubber" and thought that maybe this is why I've been bottoming out. But now that I tried to put the "mounting rubber" back in, it doesn't fit. When I slide the "mounting rubber", collar, and the metal washer on the shaft, I can't even get it to come through the chassis/column. If you notice, there is a rubber seal that sits underneath the upper mount (visible at the top of the pic) that is making contact with the "mounting rubber" - is that supposed to be trimmed? I don't see how this is going to go in this way... which is probably why I left the "mounting rubber" off in the first place.

Can anyone shed some light on this?

Eggie, these are 25" fronts, 25.25" rears ground to fender lip. 500 (?) Front and 200 (?) Rear spring rates. Check out the pic.

Rear: Eibach 41148 - GC180.64.61

Alright, it comes down to this. Can someone offer input on whether part number 3 is retained or removed during the koni/gc eibach install?

gracer7-rx7

iTrader: (16)

Here are a few pics of my driver's side suspension using the M2 / Ground Control setup. I believe the only difference is the colors. I don't quite understand why you mounted yours the way you did. Seems a bit odd.

I'll try and remove that top nut later to verify what is under there. I don't think you even need the rubber donuts really.

If you only have 200 lb springs in the rear, they are probably too soft and you are experiencing "coil bind". Search on old posts by Max Cooper as he experienced a similar situation when using soft rear springs. Also, what is the length of your rear springs? 6"?

That .0500 is the spring rate for the springs. In the pic you posted, they are 500 lb springs but those are the fronts.

TypeFD

iTrader: (1)

This helps a great deal. It looks like your setup is almost identical. I believe you've got a metal washer and a rubber o-ring sitting underneath your CO upper mount, which has another rubber o-ring, metal washer on top, and then bolted to the chassis. You've got your shock going through that and aside from the color and different type brace, the top of your column look identical to mine. I don't see any stoppers, bushings or anything else...

So the "mounting rubber" is supposed to be left out then?? Weird... I'll see if I can dig anything in the posts. Although I cannot imagine it would be that... this setup came off my old FD that experienced none of theses issues.

P.S. The shock in my picture is collapsed by the way to give me access to the top of the shock. Did you intentionally leave off the aluminum collars that go on top of the c-clips. If I would've done that it would've been a lot easier to work with the shock... and it wouldn't have widened the bottom of the coilovers.

Just got off the phone with Eibach and then Ground Control. Here are my spring specifications, deciphered:

Fronts: 0600.250.0500 (Eibach Native No) = 6" tall, 2.5" diameter, 500lbs spring rate
Rears: GC180.64.61 (GB Native No) = 7" tall, 2.5" diameter, 350lbs spring rate

So, correction to the above...

Alright, so I put everything back together, re-adjusted heights and tightened koni's to the firmest position possible, half a turn back on all four. It's not bottoming out as bad, but still does...

Another thing I noticed is that when I first bought these shocks, the firmest setting on these was incredibly stiff. The car was bouncing like you wouldn't believe so I had to almost always keep it at one turn from the softest setting. Now, the firmest setting feels like what it was back then...

gracer7-rx7

iTrader: (16)

Not sure if I understood you correctly but there is nothing extra under the upper mount. The rubber isolator you see is part of the upper mount just like yours looks in your pic.

If by 'o-ring' you mean that rubber donut, you are correct.

The top mount is the only thing bolted to the actual chassis via the 3 studs protruding from the top mount of the coil over.

Seems like it. This setup uses a couple less parts than the regular upper mounts do.


No idea what you mean by "mounting rubber".

[/QUOTE]

The spring perches are not necessary using the GC coil over kit. I really don't understand why you left yours on. The collars sit on the c-clips and the springs sit on top of the lower adjuster negating the need for spring perches (which are needed for the regular style, larger diameter springs).

When you put weight on the rear of the car by pushing down on the bumper or something, how far does the suspension compress? Do you have an assistant that can push down hard enough on the rear while you try to observe if the rear springs bind?

TypeFD

iTrader: (1)

"Mounting Rubber" is a part identified as number 3 in the Workshop Manual diagram prior to your original reply.

Spring perches: not sure why I left them when originally installed on initial FD, but never thought about it again. I ended up removing them this time however.

Spring Compression: haven't noticed anything abnormal here as far as travel is concerned. Don't believe the springs bind but can double check.

TypeFD

iTrader: (1)

Mahjik, thanks for the pm, your boy tells me going up to 450 spring rate in the rear would probably be better.

Giving it some thought, it probably wouldn't hurt to start with the bushings, etc.. first. I've never had these issues on the previous car the shocks/springs came out of so there might be a chance that this car's bushings are going... even though it's only got 76k on it. Weird.

I'll post updates as they come.

cewrx7r1

iTrader: (2)

Stock spring rates are 263/195 = 1.349 to 1.
My Ground Control with Tokicos are 550/400 = 1.375 to 1.


500/450 would equal 1.22 to 1 which is too soft for the front.

TypeFD

iTrader: (1)

Ok, but then according to this analogy I should be having none of these problems as my spring rate now is 500/350, which would put it at 1.429 to 1.

Or are the two unrelated?

cewrx7r1

iTrader: (2)

It is the combined spring rate, spring length, and perch height that affects positioning.

With my setup, I only can raise the front about another 1/5" but the rear can be raised about 1.5".

ptrhahn

iTrader: (9)

200# Springs are too light if that's indeed what they are.

Also, you don't reuse ANY of the parts in the shock diagram, or the spring perch that came w/ you Konis. There should be an insert in the threaded GC sleeve that rests on the C-ring on the shock body.

If you reused the wrong parts, it could also be you've reduced the shock travel, and the body is just bumping up against something it shouldn't.


FYI, 500/400 is a GREAT set-up

TypeFD

iTrader: (1)

ptrhahn: you might not have read the latest posts, I corrected myself after calling Eibach and GC for help deciphering the numbers:

Fronts: 0600.250.0500 (Eibach Native No) = 6" tall, 2.5" diameter, 500lbs spring rate
Rears: GC180.64.61 (GB Native No) = 7" tall, 2.5" diameter, 350lbs spring rate

Also, cleaned up and removed koni perches so it looks just like the gracer7-rx7's pictures. C/O's sitting at the highest Koni C-clip setting to allow for maximum shock travel.

cewrx7r1: thanks for your reply although I'm not quite sure what you're referring to here... elaborate?

==

In any case, my bushings are I busted now so I'll have to replace them. As others have recommended, I'll increase spring rate at the rear to 400, and then may be to 450 and see what that does.

Incidentally, does anyone have a pair of 7" tall, 2.5" wide, and 400lbs or 450lbs spring rate rear springs for an FD they want to get rid of? It would be ideal if I can opt to return them in case they don't work out.

gracer7-rx7

iTrader: (16)

If that part number is indeed for a 350lb spring, then you'll be OK with them (depending on the purpose of the car). I have ptrhahn's old setup and agree that 500/400 is a good setup for a car that sees the track often. With my larger rear sway bar the rear was more lively on those spring rates that I was used to. I had to soften the rear bar to better suit my style and what I'm used to. I'm now experimenting with 450/350 rates and the same bars. Mostly experimenting for the sake of experimenting.

I am also going to have the front shocks tested and probably rebuilt and revalved. I think they are a bit worn and the car feels a little floaty on certain roads. There is a local place that is an authorized Koni repair facility. Perhaps you should call Koni and see if they have someone semi local that can see if the shocks are still in good shape.

I'll probably have a selection of springs available once I'm done with my experimentation.

TypeFD

iTrader: (1)

Anyone can recommend where I can source these springs from. I opened a thread looking for some out there but I think I might have to get these new.


Anyone? Tired of bottoming out with my **** + I still need an alignment that I'm waiting to get until new springs are in.

Mahjik

iTrader: (1)

http://www.ground-control-store.com/...ory.php/CA=213

Josh18_2k

iTrader: (3)

im really suprised no one has told you...
you're bottoming out because you have the springs perches all the way down!!
look at the pic you posted- with the coilover completely unloaded, theres less than an inch of shock travel. all of that is used up when you set the car on the ground.
raise the coilovers!!

gracer7-rx7

iTrader: (16)

You have a point there but he did say that he "put everything back together". Wonder if he put it back together correctly...

Got pics, TypeFD?

MazdaGuy42

iTrader: (1)

Hey guys,

This has been a great write-up!

I'm in the process of up-dating my suspension. I would like to know from you guys what you think about your set-up using the Eibach with the Ground Controls.

My FD is going to remain nearly stock body wise (just updated to 99 spec) and I don't want to get banged around on the road with a rough ride. I was just thinking of some of the Eibach "sport" line springs with Tokico shocks.

Currently I have stock shocks with Suspension Specialties springs. After my single turbo conversion and front mount the front end of my car sits "High." I'm affraid that if I just buy springs the car will sit the same just lower. I'm thinking with all the weight change from adding and removing parts from the engine bay for the single swap I might need a setup like yours so it can be adjusted. I'm not crazy about the idea because I've had cars with coil overs and the ride sucked!!!

Thanks for your input...

Keep this page goin'... great info.

Dom

gracer7-rx7

iTrader: (16)

^read this thread
https://www.rx7club.com/suspension-wheels-tires-brakes-20/howard-colemans-fd-chassis-setup-723617/

MazdaGuy42

iTrader: (1)

gracer7-rx7,

Holy smokes! Thanks!!

Dom-

TypeFD

iTrader: (1)

Alright, time to re-engage this topic. Been putting in a lot of hours at work and other stuff the FD has been sitting for a little while. Now that the weather is cooling down a bit and I have some more time on my hands I'm going to go ahead and order some rear springs and put them on...

Look for an update soon!


See post #3