The Forgotten On

Probably has a larger front sway bar too!

GregBBRD

And some 1200 pound front springs to limit that nasty/useless suspension travel.

GregBBRD

Always the first step to improved handling on a 928, because it's the only simple piece to change.
Forget that 928's have crazy understeer, straight from Porsche, and understeer is even worse if you got that "limited slip" option.
Bigger and red (or blue) lets people know you are an accomplished suspension engineer and your car must now better/faster.

The Forgotten On

Real people in the know know to install a 78-79 front sway bar and sticky tires. It makes the handling a bit more... exciting

granprixweiss928

I did all my lower bushings (not shock uppers) as well in my 81 and it was a huge improvement. the fronts especially so for the improvement in spring rate

GregBBRD

If only it was that simple....anyone/everyone could/would do it!

When these cars were designed, getting .8G's out of a set of tires was an amazing feat.
The suspension was designed around that, using suspension technology that was current, for that time. (Late model ('86.5 to '95) 928 suspension was designed in 1984 or 1985 (?) and remained unchanged all the way through 1995.
That's almost 40 year old technology.
And between 1985 and now....there's basically nothing that has been "created" to improve this suspension design, but tire technology evolved a couple of times....at least. There's "street tires" that will pull 1.4G's....if the suspension can deal with it!

However, there were a few things made/done to make the cars handle worse:
1. Larger sway bars....perhaps a good thing in the rear....but absolutely awful in the front. Increased understeer.
However, most people don't drive a near the limit and thus don't know how bad they just made their car....but since they spent money....it must be better....until one stumbles into a situation where they actually "require" the car to handle properly!
2. Spring sets which increased the front and rear spring rate....with always a larger increase in front spring rate. Increased understeer.
However, most people don't drive a near the limit and thus don't know how bad they just made their car....but since they spent money....it must be better....until one stumbles into a situation where they actually "require" the car to handle properly!
3. Louie Ott sway bar stiffeners. Again, might help a bit, when used in the rear, but a complete disaster when installed on the front! Increased understeer.
However, most people don't drive a near the limit and thus don't know how bad they just made their car....but since they spent money....it must be better....until one stumbles into a situation where they actually "require" the car to handle properly!
4. Increased tire width...the sky is virtually the limit on the rear. Not so much, in the front....which is where the understeer comes from. Increased understeer.
However, most people don't drive a near the limit and thus don't know how bad they just made their car....but since they spent money....it must be better....until one stumbles into a situation where they actually "require" the car to handle properly!
5. Koni shock kits with higher percentage of front spring rate. Fantastic! Fricking 80 year old Koni shock technology. A true step backwards, with the salvation that one can crank the shocks up super stiff....so the car feel like a "race car".
However, most people don't drive a near the limit and thus don't know how bad they just made their car....but since they spent money....it must be better....until one stumbles into a situation where they actually "require" the car to handle properly!
6. Poly bushings: Some things about them good, some things absolutely terrible.
However, most people don't drive a near the limit and thus don't know how bad they just made their car....but since they spent money....it must be better....until one stumbles into a situation where they actually "require" the car to handle properly!

GregBBRD

Really "interesting" suspension engineering there.....left over from all the Porsches built before the 928, the 928, and everything made concurrent with the 928.
By using "captive" rubber bushings, which "twist" as the suspension travel, Porsche was able to increase the spring rate, as the car leaned into the corner.
Kinda cool way to satisfy the "legal eagles" who wanted all the cars made to understeer, so idiots, who couldn't drive, wouldn't die from oversteer.
The further the car rolls, the more spring rate....increasing understeer.
Driver gets frightened, lifts off the throttle, and the car quits understeering.

Magical engineering characteristic, but the slowest way possible, through a corner.

Once the lower control arm bushings deteriorate and break and no long twist, this "extra" spring rate is essentially gone and for a short period of time (during the rubber deteriorating) the car will actually not understeer as badly.
However, by this point in time, the front sway bar no longer moves freely in its rubber bushings....and make up some, for the deterioration of the lower "A" arm bushings.
The shocks are also worn out, by this point in time...further reducing any functional suspension.

The cars just feel heavy and lazy...

If anyone gets a chance, put a Boxster (or anything built after 1998) into the air.
What do the front control arms do?

Speedtoys

Maybe that wasnt so much a legal solution (The captive layered bushing) but at the same time it CAPTURES the car on excessive rebound...maybe the cool part of a progressive spring working with the linear springs..was a "Nobody ever thought of it' clean napkin idea that helped in other ways.

I'm not aware of any other car that captures a car on excessive spring rebound.

There is a highway bridge skirt that throw a car up in the air pretty badly near me, and the 928 just doesn't fly up into an odd parabolic arc..it's pulled down and settles a lot faster than the chassis did before.

Others w/o new bushes note that they would be all over the place hitting that at speed in comparison.

GregBBRD

Now were getting down to it....
Linear spring mixed with progressive spring.
Imagine that!

I can almost guarantee that with our current "test car" suspension, you wouldn't even feel that bridge skirt. The suspension absorbs everything we can throw at it, so far.

1995, 12 hours of Sebring. (This is a story I've told before.)
One of my jobs:
Go figure out why the BMW's were several seconds a lap faster than any of the Porsche RSR's, including ours.
Turn 17 showed the entire answer. (Turn 17 was very bumpy, back then....I have no idea what it is like, today.)
All of the Porsches went through this corner like they had suspension engineered by the Joker. When the tires and suspension moved, the chassis moved also. A bunch.
All the drivers, including ours, looked like "Dodger Dolls". The RSR's would pick up a front tire and in some cases, a rear tire.
The BMW's went through this corner like they were on a lazy Sunday cruise, on a perfectly flat surface. All four tires firmly planted on the ground. No drama. No chassis movement.
Sure the tires and suspension moved, but the chassis never even wiggled.

The BMW's would pull the RSR's two to three car lengths....through this this corner, alone.
Multiply this by 16 other corners....."Thanks for coming, filling the field, and paying for the event, Porsche."

That's been the "Holy Grail" for me. (I quit working on 911 race cars before I could ever accomplish this....but I never got 997 Cup Car to do this.)
Crazy cornering speeds, with amazing grip from the tires, without the driver even feeling the bumps.
Lazy Sunday drive, watching the driver behind you bouncing around inside the car, in your rear view mirror.

We're there. We have this. Russ loves it.
Is there more left?
I guess we will find out.
But it's really nice to be able to come back to this point...just in case!

checkmate1996

Well if no new shocks are available anymore, it may all be a moot point...

IcemanG17

One serious error many "track" driven 928's make is to drop them TOO LOW.....bump stops aren't suspension......

Casper has custom bilsteins with heim joints top and bottom, 1025lb springs front 400lb rear. (casper is only 2850lbs wet with me in it) I think it had a devek front bar and NO rear sway bar (it was there but zip tied out of the way)......WHY I found the suspension worked better without it....it felt like it moved with bumps and hooked up earlier so you could get on the throttle harder and earlier getting off corners.....vs with the rear bar hooked up it would sorta skip around...so you would wait for it to settle down, then get on the gas....

So in theory it should be an understeering mess....yes, if you ran staggered tires....240/650-18 Yokohama slicks front and 280/650-18 rear...also hurt peak braking.....needed a bit of trail braking to rotate....

With a square tire setup of Pirelli slicks 275/645-18 all around on 18x10's it was GREAT....I never ever ran out of "wheel"....if anything it was a bit loose, which is how i wanted it.. Granted this was at a lowly 243-265whp depending on tune.....

I do wonder how she would feel with all new bushings.....I would guess much better.....but as the best handling 928 racer I ever knew, its hard to improve on 1.6G with zero aero on used slicks.....the Estate was the single best 928 racer I built, but it was a bit tight at the limit on purpose since it was an endurance racer with lots of different drivers

worf928

This thread should be retitled to “New suspension rubber - sarcasm”

GregBBRD

Or a great opportunity for someone
who has spent the time (and money) to dyno test every single shock ever made for a 928 year and knows what is needed to improve on all of the 40 year old designs....