mmorcill

I recently purchased a 90 S4 and had Eibach/Bilstein Coilovers installed along with a good used right rear control arm (original was bent). The car had a four wheel alignment (the right way) and ride height adjusted to within spec by a reputable shop.

The problem I’m having is that the car seems react to steering inputs in a strange way and it lacks that Porsche "Balance" that I have come to know. When performing quick lane changes I have the impression that the car will change direction in two stages. The first stage of turn-in feels "normal" then with the second stage, turn-in becomes much more abrupt requiring corrective steering inputs. On long higher speed sweepers I feel like I am trying to balance the car between the two stages of steering/turning, which certainly doesn't inspire confidence. The car didn't exhibit this behavior prior to having the shocks/springs installed and it actually felt more stable with the worn shocks/springs.

Any ideas or experience on what would cause this kind behavior?

I have also leaned on each corner of the car to check out the new stiffness and I noticed that while the rear barely moves the front corners are a little soft in comparison (easily bounced).

Is this normal for the Eibach/Bilstein combo?
Shouldn’t the front spring rates be greater than the rear spring rates?

After reading numerous posts about handling improving with the Eibach/Bilstein or Koni combo, I am beginning to think that there may be something else wrong.

Thanks in advance,

Michael -
1990 928S4

WallyP

One thing to check would be the large bolts that hold the bottom of the rear shocks. If the conical washers are loose, left out or installed incorrectly, you will get the effect that you are experiencing.

If one side is loose, and the other is good, the car will twitch to sone side when you accelerate and to the other side when you let up.

At least make sure that both large bolts are very tight.

Chris

To go along with Wally's post make sure the alignment was done correctly, I had a bad one and it danced all over the freeway. Felt like I had play in the steering ...

Once you get it set up i'm sure it'll handle better than ever before.

Chris

DougM

New or old tires? Once I had new tires installed and the car felt wallowy? like I was riding on baloons. It eventually settled in.

mmorcill

I actually replaced the rears as the tires had been wearing on the inner tread but the fronts were okay so they stayed.

After reading Wally's post I'm wondering if there might be any other "signs" if the conical washers are loose, left out or installed incorrectly like sounds. I may be reaching here but I think I'm hearing a slight chatter or maybe hearing more suspension noise from my driver's side rear than the other corners. Hard to describe but it's quite subtle.

I'm going to look at the bolts and washers tonight and if that checks out I'll drive it a bit and hope it settles. I was also hoping to install my greasable sway bar bushings this weekend but until I get this sorted out I figured it would be best to wait. I'm pretty sure that the car will see another alignment soon.

Does anyone have the torque spec for these bolts that anchor the rear shock to the control arm assembly?

You guessed it, I need to order the Factory Manuals too! Did I mention that this is a great forum?

dr bob

Just for grins, verify that the links for the rear anti-roll bar are intact. More than a few of these have come apart, giving that rear hula feeling on lane transitions. Simple look-see.

WallyP

Torque on the lower pivot pin locknut is 103 lb/ft.

It can be tough to tell whether the conical washer is in there or not - I really don't want to talk about it ....

DougM

Did you use the same brand of tire as the front with the replacement. With mine, I replaced the rears only, but I needed a different tire because the old ones were no longer made. Fronts still had plenty of tread so they were not replaced. I remember that it wasn't until I did a drivers ed that they finally settled in.

mmorcill

Thanks for the replies! I checked it out last night and everything looks good as far as I can tell. I used a photo from v1uhoh's site of the rear coilover installation as a reference and didn't see any difference. I'm going to drive the car for a bit and see if this settles out.

Thanks for all the info!

JWise

I ran across this old thread as I was searching for pivot pin torque specs (I have the WSM, but pivot pin was not the term used therein on the torque spec page), and wanted to chime in on my experience.

I experienced the same issues as the OP, and also had a very noticeable "yaw" to the left under hard acceleration, with return to straight upon letting up.

This situation cropped up following a Bilstein/Eibach install last year, it had never exhibited this prior to that. I chased the problem by fiddling with the ride height and getting a four wheel alignment, which reduced but did not eliminate the yaw. I also checked that the springs were in their perches properly, the adjuster rings were oriented the right way, cone washers correctly in place, drop links weren't bent, pivot pins were straight - I was running out of ideas. Then it dawned on me that the pivot pin nuts might not be torqued properly.

Sure enough, the left one was loose. Not finger loose, but not 103 ft/lbs either. Lacking a 22mm socket and without a torque wrench that went above 75 ft/lbs, I did what Wally suggested - I put a wrench on it and made sure it was really tight. Took it for a drive, problem solved! Hope this helps someone else.

Bill Ball

This photo? It is wrong.


The conicals fit into the cavities on either side of the center hub carrier (see below), not on either side of the shock as shown above. The convex faces of the washers should face each other, not away from each other as shown in the above photo. When installed correctly, as shown below, you can't see the conicals as they are nestled in the concave sides of the hub carrier. The spaces shown around the big bushings below are correct and are established by the center shafts of the bushings. This was mentioned this to Tony here a while back, but he hasn't had a chance to correct it yet.

JWise

Good catch, Bill.

Three flats
Two cones

Oriented just as Bill has illustrated. I presume it would be visually evident if the conical washers were turned the wrong way, i.e. you'd see more of them than you should.

belgiumbarry

changing the schocks i had to renew 1 bolt as this ones due corrosion damage.

Now with the bushings both sides firm in the holders i had to push hard to get the middle flat washer between ....so i would think if someone reversed the conical washers , he could not get it all together....

Okv

Very interesting.
I have exactly the same problem as the OP (unstable, inconsistent lane change and transitional) after installing my new custom coilovers.
I will certainly have a look at this.

In my case I have also made custom spacers, I will check them as well.
Maybe they wear out.
Maybe I have chosen the wrong material for these spacers.
But I should be able to torque the bolt properly, and have a test drive to verify.

My plan as for now was to re-valve the shocks and get stiffer springs.
I still might want to do that, but it just does not make sense that the car behaves like it does, after all, those springs are much stiffer than stock, and the shocks are not that far off.

The car is on stands, so it is a quick and easy job to check the torque, and even pull the lower arm bolt if necessary.
Now, if the snow melts, it will also be possible to test it.

JPTL

Good thread & great post Bill. For the heck of it, I went back to check my work done a few years back when I installed the Bil/Eib combo. Everything looks good washer/spacer wise, but I'm about to check the torque on the pivot pin nut. When comparing my pic to yours, I can't tell if the space is larger for mine.
Is there a measurement for the amount of space or the exposed threads beyond the nut? I can't remember if the nut seats, or if you stop tightening it when the proper torque is reached.