jeff spahn

Okay so I had the ML 63 out today for a drive to get it washed. Hadn't driven it for several months, it belongs to the company I work for (easy way for the owner to have another free car). It is very "tight" over the bumps, expansion joints etc.
I had forgotten what a new high performance car feels like. We also have an S65 AMG. Took that out. It is also tight over the bumps, even for a behemoth of a car.

I want that tight feel in my 928. My car feels positively tired compared to this either of the AMGs or my Acura MDX for that matter.
I have new springs coming. The ball joints have about 50k on them. Shocks will go in with the springs. Steering rack was replaced by Ron Perry not that long ago, tie rod ends at the same time. Think Greg Brown did those so I don't have any question as to them being done to perfection.

I just want a 928 that feels new when I drive it. Where do I start?

BC

The geometry itself is what makes a large difference. Those cars you described, IIRC, have strut type suspensions, as well, though I do not know what effect on the difference they would have.

Upper ball joints need to be tight, but free to move. Inner upper a-arm bushings - no slop. Lower a-arms - they get loose over time.

But, in my opinion, most importantly other than the actual geometry (which you cannot change... without alot of money and fabrication) is the shock technology.

Our shock choices are really just low-tech.

SteveG

Jeff: "New" may mean something else to you. I can't compare to the cars you mentioned and whether they approximate new in 928 terms, aren't those cars heavier? Strictly speaking, what you asked for would be new springs over Boges, probably new bushings and ball joints,[end here]. This is complicated by the fact that the aftermarket replacements are generally stiffer than the original Boges. This is the only time I will dare to speak for David, Roger or Mark, but I believe they will tell you that Bilsteins are firmer and Koni's moreso. But you should prob call one of them and get their input. The shark is often described as designed for the "doctor/lawyer" market and most of us want a more responsive ride than what Porsche put on it orginally. I suspect I haven't helped much.

76FJ55

what are you running for wheels and tires? the tire profile especially on the S65 AMG is most likely considerably shorter than the wheels you are running (if you are still stock 16") the stock sidewall on the 928 is about 120mm a quick check on the S65 AMG find the following tire sizes F 225/35-20 and R 275/35-20. these give you 80mm and 95mm sidewall respectively. The shorter sidewall will greatly increase stiffness / road feel.

JHowell37

That tightness you desire is a comprehensive thing that's not limited to just the suspension. You'd have to overhaul every bushing on the suspension, and the steering rack. You'd need new motor and transmission mounts. You'd have to replace the door, sunroof, and hatch gaskets with ones that are fresh and pliable. You'd probably have to get one of Carl's cross braces for the top of the engine, as well as one of the lowers. Even after all of that, even if you go and give every screw, nut, and bolt, an extra turn to make sure they're tight, it will probably not be as tight as a new car.

You have to remember that the 928 was first being contemplated almost 40 years ago. An S65 AMG goes back what? 5 or 6 years? Be happy that it can still hold its own after all this time, but don't kill yourself in pursuit of goals that probably aren't too realistic.

SQLGuy

I'm not sure this is the case. This S4 is my third 928. My first one was an '85 that was 10 years old when I got it and had about 110K miles on it. My second one was a '93 GTS that had only 21K miles when I got it. The GTS had that "new car feel."

Part of that was probably the sport suspension option that the GTS had and neither the S3 nor S4 do; but, on the S3, I switched to Eibachs, Konis, and Borbet C2 17" wheels, and still didn't have as tight a feel as the GTS.

What I want, and what I think Jeff is asking for, is what would need to be done to get that 21K mile GTS sport suspension feel into an older car (like my 90K mile S4).

jeff spahn

SQL Guy hit it exactly. That is what I am trying to say.

mickster

Assuming the rubber in the suspension is good and the steering rack is good, add new shocks & springs. Stiffer is better as mentioned above. Add in the cross braces as mentioned above. Bigger wheels and tires-but preferably lightweight alloys as you want to reduce the unsprung weight.

Then you need to corner weight the car.

Between today's struts, sway-bars and other advancements, the cars can compensate to some degree for the weight of the driver.

You might get what you are looking for...

SQLGuy

My '93 GTS was stock (except for the stereo). No special or extra cross-brace, stock wheels with tire pressure sensors, stock sport shocks and springs. Never did any special corner-weighting on it either. Tires were SportContact2s.

Mrmerlin

put on a set of Bilstien shocks with stock springs the car will ride very well

mickster

I wasn't suggesting it was modded. It was newer and that definitely plays a role. Additionally if you are talking a 10-20 year old car, even with a perfectly straight frame, there is going to be some degree of metal fatigue. A cross brace can counter some of the "twist" (for lack of a better word) that the car will make after that amount of time. But if you want get the feel, the right springs, shocks and corner weighting and everything else added will get you close.

Marine Blue

What wheels are you running?

When you do the shocks/springs you might consider changing out the bushings too. They may not appear worn but after 20 years and 100K miles the odds are that they probably are.

jeff spahn

I am running the stock flat slotted wheels on the 90 S4. I run Michelin Pilot A/S Sports.
It's just a general loose feeling that comes from aging of the car that I am trying to fix. I am sure the new shocks and springs will help. figure new bushings on the A Arms might help, new bushings on the sway bars. All that little stuff has to add up and tighten up the car.
I know the rack and tie rod ends are good and are tight as I just had it down and back up doing a MM/Oil Pan job.

SQLGuy

As far as a step in the right direction, I must say that my car definitely feels a bit more like it should after installing new engine mounts. I went with the hydraulic Anchor 2698's.

The new mounts got rid of one element of the loose, metal-to-metal, feel when going over bumps, etc.