unstable on dips - long plea for help
 

To my 993 brethren, especially those who have suspension insight, Like Bill V. and others:

My 95 has suddenly developed a weird suspension flaw, so much that I am hesitant driving it like I have in the past.
Over swells or dips in the road, the car will squirm, for lack of a better description.
Other than the squirm, I noticed the left rear is 1/2 inch lower than the left rear.
The front L/R is equal.
I am fortunate enough to have a BendPak midrise lift, and have inspected but found nothing amiss.

Car history - Had the car over 10 years, so pretty comfortable with the history, and how it drove in the past.
Approximately 6 years ago, I installed Koni FSD and 033 springs. Made new sway bar links.
Great driving after the upgrades......until now.

Test so far:
Thought the rear springs might have rotated in the seats.
Removed the rear, all looked as installed.
Springs same height, shocks responded to body weight the same.
With the springs removed, I cycled the suspension, all seemed to move freely.

After re-installation, back to symptoms above.
I pride myself on being able to tackle any issue....but I am at a loss this time,.

How does it corner? Does it squirm at the apex also?
suspect rubber parts in the suspension. When you renewed the shocks & springs did you also replace control arms, strut mount bushings, steering toe ends, rear links, etc?
<edit> and sway bar links, they really take a beating and get loose quick. It’s easy to take sway bars off and see / feel difference

Corners well, seems normal, until undulations are encountered.
Sharp bumps dont appear to cause any problem.

Removed swaybar and links yesterday while removing rear springs and shocks.

Need some clarification. First off, the springs rotating would change nothing. They are machined top/bottom flat so not like an ellipse where they would greatly change pressure by rotation?

Second, "I noticed the left rear is 1/2 inch lower than the left rear" :confused:

Correct. Roughly 25.5 lip of fender rt, 25 on left.

and the springs rotating is a concern for the 033 springs and Koni fsd. At full droop springs are a little loose.

the top mount is molded with a ramped groove. If the springs rotate, they will change the position on that groove.

At least the theory as I understand it.

Correct? No., Ok So we went from the same corner being 1/2" lower than itself to left rear being 1/2" lower than left right.

Um, ok, so would you say after 6 years of driving the springs are still in a good orientation or did one side manage itself in an orientation to raise that corner ride height by 1/2" ?

There I go, reading and typing too fast.

Upon disassembly yesterday, the springs as relates to the mounts were correctly positioned.

Reassembled correctly, installed and the 1/2 inch and squirm is still there.

What about replacement links and bushings? Is everything else original?
25 years is a lot to ask for 1990's rubber, even of Porsche origin.

Something is loose and it''s hard to tell in a static environment, These cars take massive forces so just ragging on the links by hand won't reveal anything.

how does it drive without the sway bars? you'll get more body roll in corners but does the squirm go away?

Tell us about your engine mounts.

/

Engine mounts.

I also suspected it might be that. Original mounts replaced with RS style mounts.

No change for the squirm.

It may seem obvious but did you check that the adjustable collars on the struts haven't moved and are essentially equivalent side to side?

Can you post an image of your KT Toe adjuster eccentrics? For example:

https://cimg6.ibsrv.net/gimg/rennlis...ea2c6faf94.jpg

https://cimg7.ibsrv.net/gimg/rennlis...cc52b83ae.jpeg



https://cimg5.ibsrv.net/gimg/rennlis...8456d70c7.jpeg

Earlier question about the collars. Both front appear secure and unchanged from the original install.

And I think the photo I posted was not of KT adjustment hold on.

When you had shocks out, did you inspect rear shock mounts? These can crack and fail. They can also be put in backwards (don't ask me how I know).

Chris, you may have nailed it. Below is a photo of the adjusters. After taking photos of left and right, I took an 10mm Allen and checked the bolt for tightness. The left side was loose. Not hand tight but loose.

https://cimg7.ibsrv.net/gimg/rennlis...b807d9792.jpeg
https://cimg9.ibsrv.net/gimg/rennlis...519a481ce.jpeg

If that's the case, you can mark alignment with a paint pen next time - makes it easy to check for a slip. You can also use alignment locking plates to reduce the chances of a slip.

Without tightening it, I am able to adjust the kit easily. Flops around. :surr:
I think it is time to get another alignment.

The person I used a few years ago is gone. Anyone know of a indy they trust in the Orlando area?

Hi Techman,
My thoughts.
--Somthing in the suspension settings slipped, some folks put a Sharpie pen line down the side of each strut and on the tow in and other suspension adjustment fasteners so if something slips it becomes readily apparent.
--The rubber suspension hat has failed and any loading by the strut in that corner is reduced, less expensive aftermarket replacements are available.
--The strut has failed, in theory, one should see leaking of fluid from a faild strut but this may not always be the case. If you pull the strut and look at it you may be able to see the issue.

Be sure to always measure the suspension heigh from the factory specified points as the body on our cars is not very accurate or consistant for measuring purposes,
Here is a chart that points to the measuring points on a 993:
https://www.dropbox.com/s/qtxet2j9ej...nlist.pdf?dl=0

Just some thoughts from a shade tree mechanic.
Andy

Techman,

This might not be close enough to you... I use Ramses's (sp?) Automobile Alignment on route 3 a bit south of the space center on Merritt Island. They have four wheel laser alignment rack. They have ramps if your 993 is lowered. They did my 993 and BMW M5 recently. Appointment is required

Good luck getting this sorted.

Also check your tire pressure, many years ago my right rear tire was very low and I would get a squirm every time I shifted a gear.