drscottsmith

All -

Here is what I have replaced thus far related to NVH and handling on my ‘83 US Model S:

1) motor mounts
2) tie rod ends
3) rack bushings (Delrin)
4) front sway bar bushings
5) new rear tires as one had a busted belt

I must say the car is very smooth at speed now and the steering is VERY tight (a good thing).

Here is the issue - with all of these things replaced, the car handles at speed as if I were pulling a trailer (and a big one at that). It drifts all over and feels like the rear of the car is trying to steer the front.

I know I have one leaking shock in the back so that is on the list, but my question is what else would cause the handling - it is honestly somewhat scary at speed.

My suspicion is all of the rear suspension bushings - as the ‘rear steering’ provided by the weissach axle is all out of whack due to 36 year old bushings.

Am I thinking correct or could this be some other issue?

Thanks as always -

scott

rjtw

Has the car been aligned? And is the ride height within spec?

M. Requin

+1 on alignment- sounds like you might have some toe out.

Ad0911

There are certainly some bushings worth replacing. When I took my suspension out of the car two bushkngs (that sit in the subframe) almost fell out of the arm by itself.

Hilton

Lots of shops assume its like all other cars - its not. 928 needs to be settled back down to driving-ride-height before it can be aligned on slip-plates. Lifting the car and then aligning means as the car settles (can take a lot of miles), the alignment goes out and makes it twitchy, which is likely whats happened to your car.

Also - what wheels are on your car, and more importantly, what is their offset? As too low a negative offset can also adversely affect handling.

drscottsmith

Hmmm...ok thanks all for the responses. Some more details.

Car was 4-wheel aligned by a shop I trust after the tie-rod/motor mount job. I printed and took them a copy of the workshop manual to follow - everything seemed fine. The tech did tell me that the rear camber was maxed out (at the end of the brackets). Not sure exactly what that meant but wanted to report that for further comment.

When the front end was worn and before the tire belt broke, I do not remember the car having the floaty feel. But I have nothing else to compare it to.

Any further thoughts?

-scott

drscottsmith

Oh and sorry. The wheels are the factory manholes - 16" all around - in my avatar. Tires are 225-50-16.

worf928

Did you know to tell this shop not to unload the suspension during alignment?

Did you watch them during the entire process to ensure that they didn’t?

If the answer to either of those questions is ‘no’ then they lifted the car. NO ONE, and I mean *NO* *ONE*, that works at a shop that doesn’t align 928s every day believes that a 928 won’t settle on slip plates.

drscottsmith

We did have the discussion about keeping the suspension loaded and they have the correct machine to do it, but I did not watch the entire time to verify.

drscottsmith

So been doing some additional reading on the rear alignment procedure...my car does not have any tools with it. What is the weight of the tools put together?

-scott

FredR

If you know for a fact one rear unit is shot what makes you think the others are much better? I would not rule out the impact of having one unit shot and having bushes that are shot is no good either. The 928 suspension system is quite robust but it does have a sell by date and unless all the sub systems are working as they should you cannot expect the car to handle anything like it is capable of.

The simple test for suspension units is to bounce them wherein the thing should rebound and stabilise- if it is bobbing up and down at all then therein lies a problem.

Ad0911

Try to find a shop that allows you to be present during the alignment. And talk things over with printouts from the WSM. This helped me.

76FJ55

I agree that if all the shocks are original and you have one which is obviously bad, that the others are likely bad as well. One other thing that I haven't seen mentioned if the large pivot pin in the rear suspension. if it isn't torqued correctly or if the cone washers are assembled in the wrong order or facing the wrong direction, the rear can shift continually under varying load and will not be stable.

jpitman2

I have an 83 Euro with M474 Bilsteins which will be a bit tauter than a non-M474. I have had the rear shocks refurbed and replaced the fronts with new`units(with height adjusters). I watched a 928 knowledgable guy do the alignment , and its a dream outside rough suburban roads. No handling problems up to 125mph. I would check ride height, tyre pressures, then alignment without lifting. If that doesnt fix it, suspension bushings , or something bent . When I imported mine it had to get it flat bedded to be steam cleaned underneath, and they pulled it on the flat blade of`the lower rear arm, and bent it. The drive home from the customs site was very hairy to say the least, which is what yours sounds like! Replaced the arm, aligned, all good.
jp 83 Euro S AT 57k

drscottsmith

Thanks all for the latest round of replies.

Here are a couple of answers and thoughts:

1) I know the RR shock is leaking - you all are correct in that all 4 are way past their due date.
2) When I loosened the front control arms to pull the rack and motor mounts, I noticed the front bushings looked surprisingly good to me. No dry rot or anything. I almost did not replace the sway bar bushings, but already had them so did it WIWIT.
3) I have not personally had the rear pins out...I believe the shocks are factory original so I doubt they have ever been removed.

I see what you are saying JP and honestly have no idea if I have something bent or not (nothing to compare it to...it kind of makes sense that the camber adjustment is maxed out and maybe that is because something is bent). Can you send a pic or in the WSM show what I am looking for/at? I have no history on the car so no idea if it has ever been strapped or pulled by the suspension arms.

-scott