GregBBRD

I'll tell you...I learned more about camber and toe (through the entire range of suspension travel), after I bought my own $80,000 alignment rack, than I think I learned the entire rest of my life. Plus, this data is incredibly accurate and fairly quick to gather, versus the other methods I have used, most of my life.

Upper and lower control arm angles primarily alter the camber, as they travel to their relative extremes....virtually no affect on the caster. And the arrangement of the 928 control arms make for much smaller camber changes than say a lowered 911, that we don't have to fight this battle as much as we have had to do on prior vehicles I am very familiar with. Toe change is a very interesting "study", on a 928. There isn't very much, until extremes occur, so under "normal suspension' travel "bump steer alterations are not really necessary. However, on this particular vehicle, with the suspension travel we have available, we do utilize a custom hand made bump steer system, with custom tie rods and monoballs to keep toe changes to a minimum.

Like on any track car I've ever worked on, I set camber completely from what I see on the tires...temperature readings are almost completely worthless unless they are "live, in real time", from sensors (which we do not have, on this car).
Checking tire temperatures, once the car slows and returns into the pits tells more about how hard the brakes are being used, rather than very much about the tires (You learn stuff, like this, very quickly, when you are sponsored by a tire company, like we were for several years when running the air cooled RSR's.) We had multiple "private test days" at Willow Springs, where the tire company would bring an entire trailer filled with a dozen different compound/construction tires and we just "turn" endless laps, doing tire testing.
Tire temperatures can be valuable to select the proper compound of rubber hardness, but this, too, is generally very obvious thing, visually.

Alignment turns out to be of tremendous importance, especially at Thermal, which has a very "wicked" right turn, which is infamous for chewing up the right front tire. And this corner is present on every different track configuration they will ever set-up (there are several.)
We do have a "mystery" phenomena in our extreme GTS, at Thermal. As of yet, we are not having the same issue with destroying this front tire, as all the other cars do...this is leaving the "people in the know", at Thermal, scratching their heads.

Speedtoys

Got it, and final question, I KNOW I will be surrendering my Devek front bar with this, what about my 'red' "i forget who makes it" rear bar?

And..waiting for Kyle to text me to drive down.

GregBBRD

Truthfully, my suspension mentor, my test driver, and I favor using the shocks and springs to control the car and like to use a sway bar simply to move some weight from the heavily loaded tire to the lighter loaded tire, without allowing the sway bar to ever "lift" the unloaded tire. (The theory being that four tires, on the ground, are better than three tires on the ground.) Additionally, unless one hits a bump which affects both tires, at the same time, a stiff sway bar adds harshness to the vehicle, which is just the opposite of what we are trying to achieve. (Better handling, with less NVH.)

Truthfully, I brutally learned this lesson at the 12 hours of Sebring, years ago, as the BMW's just drove away from us, smoothly going through the corners (with all four tires on the ground), while we "pogo sticked" our RSR's through the same corners (with 3 tires on and off the ground.) In some corners, the BMW's would "pull" an entire car length, on us. Simply beautiful to watch the BMW's and very painful to watch all of the RSR's.

A very "enlightening" moment, for me, as the chief car set-up guy....I had a complete lack of pieces, that would help me with this issue....and I had a stack of shocks and other pieces.

(Worth noting, I'm running stock sway bars, in the Extreme GTS.)

Not discussed here (nor anywhere else) my test driver also has a 951 (originally equipped with the "insane" Koni M030 suspension package), which is also undergoing a large suspension development program. I think we/he has bought every single sway bar, from the absolutely absurd "Weltmeister" sway bars down to what came on a 924.
And, as development has continued, we keep "going down" in sway bar size....

depami

I too am considering suspension work on my 86.5.
Is there a list anywhere, with part numbers, of "must replace" parts to return a car to original performance?

ROG100

Surely this breaks down into two categories.
1) How can I replace my stock 928 shock & spring setup without breaking the bank?
2) How can I transform my stock 928 shock & spring set up to a truly up to date supercar technology.

Most of my customers want #1
Generally price is a prime consideration.

depami

Roger that!
I'm in the #1 category.
I'd like to get my car as close as I can to "factory new" suspension without "breaking the bank".
Can you email me a list of what you'd recommend?

Cheers,.

Rob Edwards

Here's the full monty list for '86.5 to '95, contingent on condition of what you have:

streetsnake

I’m around a 1-1.5. Hopefully not needing to do any fabrication.

Speedtoys

Springs "if height cant be made"...is IMHO, a shrunken upper shock mount..and really really rare to need
Everything else..do it

Speedtoys

Updated Here:
https://docs.google.com/spreadsheets...it?usp=sharing

Note, this was HALF this price when I did this...3yrs ago?? DO it while you can, and while the parts are available...

GregBBRD

Roger:

It's actually a bit more involved, for us, that just the two options, currently:

1. Stock suspension rebuild. This can vary from a simple shock change to a complete overhaul of all of the rubber parts, depending on client and budget (most 928's desperately need the rubber parts replaced.) Optimum ride height in the 160mm range....somewhat dependent on what shock absorber is chosen.
2. Fairly straight forward modifications, to improve the handling and improve the NVH. Allows the car to be lowered into the 150mm range. Reduced understeer because of modified pieces which allows the car to be properly lowered and still have front suspension travel without riding on the bump stops (This is what I'm proposing for the OP, in this thread.)
3a. Street/canyon racer suspension, with greatly improved NVH. Oversteer characteristics virtually gone. With sticky tires, the grip exceeds most people's desire to go at the speeds required to "make the car" get loose. Wider than stock tires and wheels allowed, although rear wheel/tire widths must be reasonably matched with the front. (Jeff Mohler will be getting this version.)
3b. Same as above, with custom adjustable shocks for both bump and rebound. The shocks have "altered" dimensions to allow lowering the car into the 140mm range. "Tune ability", for the individual driver's ability very high and can be changed, as driver ability increases.
4. Street/track car. Good NVH. Adjustable custom shocks for both bump and rebound. Spring rates increased. All of the suspension mounting and spring parts are changed.to custom pieces. Virtually unlimited suspension travel. Getting this level requires a Non Disclosure Agreement and the vehicle must be modified in our shop, as the pieces and technology is way beyond anything available, from anyone else. Designed for very aggressive and wide "low wear number" tires. Factory sport seats are a minimum requirement, along with 5 point seat belts. Roll bar highly encouraged and it can not be bolted to the weakest part of the car (the floor.) Minor front chassis stiffening required. Roll cage not required. 350+ horsepower very desirable. Highly functional, true 40%, limited slip required.
5. Dedicated track car/possible to drive to the track. Designed for a car with wide slicks. Significantly increased horsepower highly recommended. Shocks have remote canisters and are triple adjustable. All of the pieces used in Version 4, with significant spring rate changes. NDA required and vehicle must be modified in our shop. Roll cage and chassis stiffening highly desirable. A track test day, with the driver, will be required, to set-up shocks/alignment around the driver's ability. Professional, private test driver possible for hire, if desired. (He will explore the limits with the driver, but the set-up will revolve around the owner/driver.)

Speedtoys

Yes..I would like the 3a.

Hold the cilantro.

GregBBRD

A very, very interesting part.
We could get together, with 6 other highly technical people and debate this part, all night long.

New, it certainly "absorbs" some of the actual spring rate (of the main spring), as it compresses. Old, this is not the case and understeer is increased, since virtually none of the actual spring rate (from the main spring) is absorbed, but simply transferred through the rock hard rubber.
New, makes obtaining lower ride heights more difficult and the car must sit for about a month (or be aggressively pulled down over night), for this part to compress enough to get the correct ride height. While our 928's might have left the factory at 180mm front ride height, they certainly were not this high, once they arrived here, from an ocean's voyage. This part compressed, along with the movement of the lower control arm rubbers.

The really bizarre part about this part is that it has the same part number, throughout all of the different models.
This borders on the absurd, from a suspension technical point of view, when one considers the difference in front corner weights as the vehicles evolved.

Worth mentioning, in both in Version 4 and Version 5 of our current offerings, this piece is completely eliminated and substituted for something much easier to tune the car around...completely dependent on corner weight.

Speedtoys

Just when I see people talk about "had to adjust because of sag"...then I saw the ~1/2" difference between an old upper mount, and a new one, and you could take a pen and feel the difference between the two...

icsamerica

I just wanted to add that the roads where you live are going to be a major factor in what's right for you. For example here in my part of the North East where the roads are awful. The Koni's with modified spring as I detailed in an earlier post are very tollerable and offer up good capabilty and the necessary ground clearance. On California / Florida (my expereince) roads you should and could go much further becasue the roads are better, people drive much faster and you could use the extra capability and perhaps some additional lowering without beeing irritated by suspension harshness. I recently did a 1400+ mile trip from Vegas to Anaheim to LA then on to Sandiego. I was shocked how good the roads were. If traversed those roads I'd certainly choose a much more firm and capabily setup to daily. The banked sweepers and smooth roads of CA are nothing like what exists here in my part of the North East. In fairness to all those who make recommondations they are generally doing so with good intensions but only you could know what right for you where you are. It might take some travails to figue it out but that's part of the fun.