wino5150

Help! I have recently placed a Koni/Hypercoil package purchased from Carl at 928 Motorsports. I'm very please with it, and his customer service is excellent. One snag... In order for the car to be at 'Porsche Spec' ride height (on stock rims and tire size...as they recommend); the rear shock collars are approximately one inch different in height. The driver's rear collar has to be raised, so as to compress the spring in order for the car to ride even. The springs have been removed and confirmed that the rates are the same, which they are, as well as the length of the springs. The car has never been wrecked and the frame appears true and easily alignable. Somehow, the driver's rear sags and for life of us, we don't know why.

Thoughts...

Slantnose!

Hello.
Same here...
I'm running the 600/400lb rates and it got even more extreme once I tried to corner weigh it.
I found that the fronts can't be equal and that allowed me to back off the rears somewhat, though.

glork98

You've got the front messed up. It's easy to get the ride height right and totally mess up the corner balance. What happens is that the LF and RR (for example) are very tight (coils shortened) and the RF and LR are loose. The heights are right but the balance is off.

Slantnose!

Yep, you're right.
Once up on the scales, everything made a lot of sense and I was able to get within 1/4", too.

wino5150

That's the plan...I'll corner balance it. That was suggested to me several weeks ago, and even Carl mentioned that too; but I was given the impression that if you return the car to spec height using the designated frame points, then that would be the same. I'll have it balanced and we'll see how the heights change. It would only make sense I guess, that if I have to put more pressure on the spring using the collar on only one side, that the balance of the car is not even.

Thanks for the reply...

Earl Gillstrom

This is from the miscellaneous ramblings section of my web site.

CORNER BALANCING
I have found that when properly balanced, the spring perch adjustment nuts for most 928s are the same height on each side of the same axle. Apparently Porsche springs are very accurate. I therefore recommend that during ride height adjustments, you make the spring perch height the same on each wheel of the same axle. You may end up with the ride height slightly different from side to side, but the car will be close to corner balanced and the difference will not be visible. Keep in mind that the car is not the same weight on each side (passenger side heavier on LH drive cars) and the sway bars may not be perfect. Also, if you have Louie Ott drop links, un-bolt the lower rod end attachment from the lower control arm during ride height adjustments and adjust the length so that the bolts just slip on when you re-install them.

bwoyat

When I put in my bilstein/eibach a couple of months ago I went 155 front and 160 rear. When I took it in for alignment and corner balance the tech told me it was like it was sitting on an unbalanced table top! He did the corner balance and it handles extremely well! Looks better a bit lower and handles great.

p.s. - bought some chin plates from 928MS because it's lower now and have heard several scrapes since installing then. Good product to install so you don't rip stuff off.

Brent

mark kibort

you guys are funny. corner balance is not that far off if the car is visual. worst case, you could have cross weights of a 150lbs difference. scot was 125lbs diff and he ran 4 seconds faster than Dean K did in his race car at laguna. the point is, his car handled great, but it will have some better handling characteristics if balanced better. It is no way noticable on the street, especially with street tires.

as a note,ive built 4 race cars (or cars used for racing). when ride hight is set at near even per corner, its going to be pretty darn close to start. if you use my settings, you will be pretty close to right on. generally, when the ride hight is even in the front and back, the rear passenger corner is light. raising that corner by about .25" gets this pretty close. Then, there is a diff with a full tank, passenger, etc. You see this corner balancing stuff is really silly for the street!! dont waste your money.

mk

wino5150

I would agree Mark, as I've been told the same...'don't waste your time if your mostly on the street', which I am except for 5-7 DE's per year planned. The issue arose when we 'height balanced' the car using the referenced bottom frame points, and noticed that the perch collar on the driver's rear had to be adjusted almost an inch higher (compressing the spring), in order to make the car almost even in the back. I thought that the springs were mismatched, but upon measuring them, they were within 10lbs of each other. I just can't figure out why I have to lengthen the distance on the right rear...there's got to be a weakness somewhere or the car is really out of balance. Perhaps the left front is too high...we'll see. I will be balancing the car using the Ohlins shake rig hopefully next week. Any other thoughts, just let me know...

WallyP

"when ride hight is set at near even per corner, its going to be pretty darn close to start."

Well, perhaps, perhaps not.

If you take a 928 that is corner balanced and at the correct ride height, then crank the left rear up an inch, then go to the right front and adjust there, you can get the ride heights even, but the corner balance will be screwed...

As Earl said - if you start with the spring perches adjusted evenly on the front, and adjusted evenly on the rear, and keep them even as you set the ride height, both ride height and corner balance will be close enough for the street. This assumes that nothing is bent (like sway bars or mounts).

wino5150

Wally you're right I'm sure, but that's the problem. When you adjust ride height to the factory specs, the left rear perch has to be made an inch higher than the right rear in order for the frame to be even from the floor. That would tell me that there's either a weak spring (not...because we checked it), a bent sway bar or link (not...because we checked them) or that there is the incorrect weight on the right front (maybe, and that's what I'm assuming). Until the car is corner balanced, we won't know. It's frustrating as heck that's for sure. Any other ideas...I'm all ears...otherwise...

Keep you posted

mark kibort

Wally, its more in the "perhaps" range.
IN setting up race cars, i can tell you it will be very close , but your point is well taken on the cross weights . However , even at a first shot, 100+ lbs off on cross weights the car will be FINE on the street, even with spirited DE driving. like i said, what about passengers, load, gas levels, etc. you are going to be more "screwed up" for other factors than ride hight or corner balancing.

The point is, ive been hacking away at springs, eye balling ride hights and it makes for a car that will handle just fine. with a 928, more so than most any other car, if you start with all the components at pretty even adjustment levels you will be in fine shape. i think you would have to raise opposite corners to a pretty high level to "screw handling" up too much.

for street driving, dont worry about it. just set it and go.

mk

928nut

wino5150 - I share your pain and frustrations. From what I'm reading here, the uneven adjuster height for even ride height must be more common than one would think. In many cases it goes by unobserved, focus is on getting even ride height. I have been tweaking my ride height for 3 weeks now, after putting on 16" rims and new tires, had 15" on before. I also revamped the suspension on my O.B. - out with the old, in with the new Bilstein/Eibach setup, S4 sway bar with greaseable bushings and adj. drop-links. After couple of weeks of screwing around I thought I was done, height set more or less even, near the minimum per spec.s Then I noticed I had two diagonally opposed adjusters cranked right up to almost maximum they could go and the other two diagonally opposed corners virtually at minimum. I was dumbfounded, asking the same question you are, WTF is going on here ? Is my body warped/twisted, are my Eibach progressive springs so crappy ? Had to take time out and think about it. Eventually I refused to believe either one was the culprit and began to lean towards the process of adjusting the ride height. I decided to go back, brought all adjusters more or less even and started all over again, this time being very meticulous, moving one corner at a time, measuring/recording results, making an adjustment, measuring / recording results, ..... on and on. To my surprise, I was able to get even ride height to within 1-2mm with adjusters virtually even as well. Hard to believe but there is a hole lot of strange interdependent stuff happening there as you raise or lower any one corner. It is a lot more complex than I ever thought.

Just my 2 cents worth based on my experience.

\\\|///
(@ @)
o(_)o -- J.S.

'79 O.B.

wino5150

Good point and thank you all very much. I guess my dilema is that I've got three perches all about the same, and the left rear cranked up an inch higher. Why? I just got off the phone with a good friend who races PCA and NASA and I respect very much. He said the same that MK was saying, which is unless you're going to control fuel load, spare tire, passengers and other things, just get the ride height close enough to even and leave it alone. I may have an instructor for several more sessions especially at tracks I've never been, so what do I do about whether or not there will be 200lbs. on the right from time to time. It's just that one perch adjuster being so far different from the other three that bothers me, so I was going to put it on the scales and see how far the car is off from balance. If it was way screwed up, then I was going to adjust the perches as needed. Then again, the car appears to handle very neutral as far as I can tell; but how much can you really do on the street?

Earl Gillstrom

Roland, Are you sure that your floor is level? I have never seen a level garage floor.
If you are unsure, go to my website for procedures to level your floor for alignment and ride height.
I think it is also in miscellaneous ramblings.