ptuomov

By solid bushings, do you mean in the joints that are in principle perfectly aligned and only have one degree of freedom, or joints that move all over the place? (Notice the precise engineering terminology that is a good indication of my understand on the topic.)

What do you use as the top spring/shock mount? The stock piece, the 928 Motorsports no-join solid part, a jointed solid part such as the one from racersedge, or something else?

tv

This happens all too often on technical issues - many opinions with some completely contradicting others and NO resolution. I have read more threads than I can count on the ideal suspension here but no real final formula. There should only be 1 optimal set-up for street use where the car has ZERO dive on braking, ZERO body roll on fast on ramps, ZERO porpoising, while at the same time taking ruts, holes, etc with a solid, quiet, non-jarring thud.

The 928 should handle/feel as good as any car on the road due to it's 50/50 weight dist., low center of gravity, and suspension design and hardware.






Seems to me that the ratio thing is a constant for all our cars so all we need is to figure out the right pound rate of the springs and the right damping rate of the shocks.


Springs -- 1200/600 at least maybe as high as 2000/1000

Shock Damping -- much less than what some use.

Can we narrow this down and then have the final set-up carried by one or more of the vendors. It should not be too tough to replicate what cars like the 997 do, no dive and a nice non-jarring subdued thud on bumps.

hacker-pschorr

Have you seen Mike Simard's web site?

http://simardracing.com/Suspension.html

I would beg, borrow, and steel to have this on my two 928's.
I'd pay for it too

rluvsporsche

ptuomov,

I too have this setup on my '87 S4 5-speed (stock) with sport option. Street/Sport front 500 rears 350. I've driven 09 997CS sport setting this is comparable to ride quality. IMO the 997CS was a little harsh just because it has lower profile tires. The only I don’t have on my car is the "Billet Spring Perch". Compared to the sport option my car this is a definite update although I took possession of my car when it was 12yrs old that being said don’t know how it compared from the factory. I've used it in DE events, SITM dragon path and very impress. Daily and long driving are great. My tire size are 225/40 18 and 265/35 18, don’t know if this matters in ride quality. If your within my area your more than welcome to drive the car.

Lloyd

I run with Racer's Edge Track Car Spec- Adjustable LEDAs with 2000lb/750lb

FBIII

I don't think there is one perfect setup for track or street use. Some drivers prefer softer springs and more bar while others prefer the opposite. Shock dampening is another area of driver preference. About 30 years ago I was "trying" to setup a DB4 Aston for track use. At the time Dick Guldstrand and Herb Adams had contrasting opinions about how to setup Camaro's and Firebirds for track use. I found this interesting reading as the Aston was also a live axle rear suspension and the vehicle weight was near that of a Camaro. Guldstrand preferred stiff springs and the use of swaybars as a means to fine tune the setup, while Herb Adams preferred the use of very stiff sway bars and softer springs. It was interesting reading.

tv

Yes I had seen that in the past, but I don't want to rebuild the entire car just replace the shocks/springs. Will those shocks mount on factory arms?





Very Nice looking






Anyway Mike is showing 2000/950 spring rates which is way, way different than Rluv's 500/350.


FBIII - there is one right set-up for optimal performance-car feel for the street. Now if someone prefers the ride of a 1973 Eldorado then they have different taste's altogether. The optimal ride is what all the top manufacturer's try to achieve today from the factory for high end SOPRTS cars.

I already described the optimal ride ZERO dive, Zero roll, yet not jarring and there is only 1 way to achieve that. I want to know what that is once and for all.

tv

When I replace my shocks/springs which I will do - I want to do it once, I want to do it right with the minimum amount of hassle, and I want to be able to adjust the height so that my car sits low. And when I take it for that first ride after it has settled I want to smile and know that I have the best ride that a 928 can produce.


Who can disagree with that?

ptuomov

tv --

So how would you go about figuring out what that optimal setup is?

One could try to rent a device like this for a little while:



http://www.racersedge-inc.com/racers...0?open&id=12.2

Then have professionals operate it and analyze data, trying out a large number of different kinds of components and setting. I don't think the whole project would be that expensive, probably just about $50,000.

Given that thousands and thousands of aftermarket suspension kits are sold every year, there's an obvious profit opportunity in here for all the vendors. Also, after spending the $50k, there's no risk of anyone copying the setup that really works and selling it cheaper. Finally, it will be trivially easy for a consumer to tell right away who's actually done his homework and who's just slapping parts together without any testing or analysis whatsoever... ...just kidding. ;-)

But seriously, does anyone have an idea how to cost effectively implement some sort of logical test plan to develop the right suspension kit for a fast street car?

Best, Tuomo

Cheburator

The joints don't move at all as there are none. I have the shock, then a leda spring cap and then the large porsche spring cap, and then carl's solid bushing.

ptuomov

Naively, I'd think that as the suspension travels something has to give. Some people ahve suggested that this setup will force the shock shaft to bend and will wreck the shock. Is this not the case?

tv

For street use-only, which is what I care about, it is understanding the principal functions of the parts involved, some common sense, and some experience.

The best way in Fantasyland would be to have 5 or so same year 928's with the same wheels/tires and different spring/shock combo's and drive them over the same streets back to back.

The best way to do it in the real world is have guy's like Mike explain that valving of the shocks is leading to harshness and guy's like Hilton reinforce his position like he did. AND for everyone to leave their ego/pride/profit motive at the door.

Hard springs / lots of adjustability for ride height (in mikes photo I linked)/ and an adjustable shock with a range in the lower numbers - seems to be the direction this should go.

I am reading and trying to absorb this right now - http://rennsport-systems.com/events/...1-suspensions/

Also it makes common sense to me to keep a rubber type material in the A-arm bushings to interrupt metal on metal noise/vibration from transferring to the car body.

ptuomov

I tend to agree with the caveat that I don't know what I am talking about.

What's your view on the top mount of the spring and the shock? It seem to me that there's a shock and a spring between the wheel and the body and therefore there's not much of a NVH concern with a solid, jointed top mount.

Cheburator

Not on the 928 - the shocks travel directly upwards... What does NVH stand for?

ptuomov

Really? It doesn't appear to be the case based on photos, but I have to admit I'd never actually paid attention to what moves where and how when looking at the front of my car.

Noise Vibration Harshness.