ew928

Since Bilsteins are a gas shock, instead of a simple hydraulic shock.
Will refreshed Bilsteins have a higher 'spring' rate than the old one.

As in will the car be higher off the ground when set back to the old height settings?
Not sure if Bilsteins settle after aging.

Ispeed

EW, I don't think there is any height difference. I am able to push the shock shaft in by hand, so there can't be any extra help there for the springs.

worf928

Don't worry. Carl has some pre-SITM maintenance requirements. I'll "fix" it for ya while I'm in there....

Ispeed

Well, got my stuff back and installed. I took some of my favorite roads and have to say it is a huge success. Very very flat ride with less (almost NO dive) dive under braking and a nice firm ride. I still think it is street-able all day long, just not for city driving with Boston pot holes. I will have more to say when I have tested more and done some bumpy higher speed stuff.

The few rides I have gotten in GT3s have made me want a suspension with that feel, where there seems to be only 1" of suspension movement but still not rigid. I am there now, with the 18" lower profile tires it all seems like a good match: sticky rubber, firm suspension, totally controlled ride. The tires will start to give before the car loses composure.

I do believe that the Bilsteins we get are valved for stock springs, so even the progressive Eibachs are too much spring for them- that is why they feel 'bouncy'. The stock springs are about 300 front and 200 rear. the Eibachs get as stiff as 560 front and 400 rear, but have some softer rates before that.
I am a huge fan of the hypercoil springs because they are not progressive, and you don't have 1-2" of mush before the suspension gets firmer.

My friend has new Bilstein/eibach on his GT so a comparison to that original set up is easy to make.

p.s. I asked for 40% more low speed compression and 50% more rebound than standard valving. Low speed compression affects dive under braking, G-outs and dips in the road.

One happy addict here!!

BC

Very nice.

Bill Ball

I may do this as well. There are some aspects of the handling, such as managing road undulations at VERY high speed (145+), where the Bilsteins do not damp well enough, so the car does not set right away but oscillates after being upset by the bump. I have stock springs, and I expected the Bilsteins to control this better.

Thanks for the report and please update as you use them more.

Ispeed

Just another driving report:
The car is definitely stiff, and very communicative. At legal speeds, you really notice the stiffness, but when pushing harder braking and cornering it feels great. You can brake late and corner hard with minimal body roll and nose dive.

This is how I have wanted the car to feel all along and I am very happy about it. It now feels like a "serious" sports car, and not just a luxury cruising GT. I think the 928 is such a competent design that is so ready for the "GT3 suspension treatment", and you will still cruise in comfort at 80 down the highway in leather, a/c, and quietness.

I think most people would be better off with just Bilsteins and stock springs than the Bilstein/Eibach package. I am convinced the Bilsteins just don't have enough dampening for stiffer springs without a re-valve. There is always the adjustable Koni option, though I don't know much about them.

I am also now convinced that the progressive Eibach springs are poop because of how they have a soft mushy feel before they get into the stiffer portion of the spring rate. I bet that instead of 600/400 Hypercoils you could go like 450/300 and have a compromise that is still a big improvement. The shock valving could then be stiffened to your taste with more low speed compression and rebound and not be as harsh as mine.

p.s. I am going to add the Carl Faucett lower frame brace (and back off the camber to like 3/4 degree), and maybe later the steel upper control arms that eliminate the rubber bushings.

The_Remora

Awesome Carl, glad to hear the revalve has worked out so well

Just recieved my new Bilsteins and a bunch of other misc. maintenance parts. GT springs from Rob arrive this Thursday. Anxious to find some time to wrench on the 9-2-8 and get my own suspension sorted so I have at least a fighters' chance of keeping up!

tomcat

Carl,

Do you have any idea how close you are to neutral (handling)? Also, what you are running in terms of the rear sway bar. Stock?

mark kibort

Sounds like you figured it all out interesting to see how it feels on the track now.
scots was the koni set up (OEM replacement) with the eibachs, but we cut the springs to be near 650 450. its very close to my car, and i cant really notice a differnce except it is a little bouncier. (needs revalving like you suggested) But, its very driveable /raceable.

I dont think carls set up will allow you to run less camber. its an interesting chassis stifening device, but i dont think im convinced that it would do anything to allow for less camber. I did some tests with the 1.8 degrees i run at the track, ran down a 1.6 G turn at Sears point and via video, didnt see the amount of flexing that would be happening to cause a .5 degree of camber change. (ie about 10mm of movement or almost a half of an inch is what would needed to be seen to cause this kind of camber change)

check out the front wheel movement in this video
http://youtube.com/watch?v=sjbhDRkGkcw


mk

The_Remora

Been toying with the idea of cutting a coil +/- off of my springs; will have used GT/CS springs up front and S4 rear springs @ rear, in conjunction with my new Bilsteins. This will be primarily a street car with some DE days down the road. Have any of you found any drawbacks to the way the springs seat with cut coils? Any recommendations on cutting coils (or not) for that application? What are the pros and cons? I've been advised that doing so could cause problems with the springs seating, etc, so I want to learn more about this before I screw something up. Thanks.

mark kibort

The unique way the stock springs seat, allow for no draw back in front and only a slight issue, if a full coil is removed in the rear. that drawback is seating the coil after you have raised the car , and the rear end is in full droop. scots car has this issue, but its not really an issue at all as the coil will seat itself when lowering the car. (the lower seats like the front, but the top might be off a little, until the lowering of the car snaps it in place. Its really not an issue)

The front coil ends up looking the same way as the stock coil when one coil or even half of a coil is removed. the last part of the coil fits into a cut out in the purch that holds it in place. by looking at scots cut springs, you would be hard pressed to notice a differnce visually. the effect is about 150lbs greater spring rate, if i was going to guess. (and it reduces the spring preload, so you can raise and lower the car more easily)

mk

drnick

i am running revalaved bilsteins as well after the same kind of learning curve - finding them too soft with a 550/350 lb spring combo. i had the valving done at the same time as upgrading the springs to 650/425 and it makes a huge difference. my shocks came back with the new compression/rebound numbers on a sticker on the side of each shock, did you make a note of the actual numbers they set them to? im curious as i still think i could do with more rebound.

Ispeed

I have been trying to get the shock dyno and data from them, but it is hard to get Ramon the tech on the phone.
I will try again and post what I get.

p.s. I had previously talked to Bill Hinsdorf who was replaced by Ramon, and he had suggested an additional 15-20% both compression and rebound. I am glad I went with heavier numbers as it feels right.
In my old life of racing motocross, understanding suspension is of utmost importance. Settings that work for hard pack dirt will be terrible on a sand track, and balancing front to rear affected cornering and handling a lot. From the mid '80s onward the suspension had gotten more and more sophisticated and you had to keep learning to stay up front.
The big difference with the 928 is that you can't tell much until you start pushing the car really hard, which you really can't do much on the street. If you drove the speed limit or live in a state with straight flat roads, old tired Boges would feel ok.

Ispeed

Well, I just got a dyno sheet with numbers from before and after. Of all the numbers,
Max force before 1927.80 N, after 2713.31 N. (compression?)
Minimum force before 4006.49 N, after 4786.73 N (rebound?)
I will scan this stuff in and post, pretty complex.
Carl