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Question Help - ride height / lowering

First let me thank Noah P, Wil Ferch, dd74, Jcon and others who responded to my earlier post. Great advice all. Now my issue of the day.

Ride height measurements are as follows:
left front 26"
right front 26"
left rear 26.25
right rear 27"

All measurements were taken on dead level ground after bouncing the car a few times and letting it recover and settle down.

From the rear the car looks a little crooked - 3/4 inch is pretty obvious.

Not noticeable in the ride

What is the remedy? Could this simply be a torsion bar indexing problem?



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Dan

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Old 01-02-2005, 04:33 PM
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measuring from the fenders is only a ball park since manufacturing tolerances will allow differances side to side. I did not see your other posts but I am assuming you know the rear is adjustable? You dont have to re-index. My car had a similar issue when i bought it. It had supposedly been corner balanced and I wonder if that caused the "lean". T bars can sag just like springs, this could be the problem. When I put new racy T bars in I set the height level. I am interested to see how mine comes out when I corner balance. If you search there is a thread where some scanned in a home guide to aligning/height adjusting a 911. I found it very easy to use and make sense of. search for Ray Scruggs and I think you will find it.
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Old 01-02-2005, 05:21 PM
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Hi Dan,

I just spent a couple of days replacing my torsions and setting ride height. 3/4" variance between L/R is way too much a difference. If you have "maxed out" your spring plate on the 27" side, then you've got to re-index the torsion bar. Also, I found that bouncing the car up and down is NOT enough to settle the suspension. To get better measurements, I bounced the car up and down, then rolled the car forward and back, then checked the heights again (remember that when you raise the car off its wheels then lower it, the tires have not come to their natural resting spot). Once I "think" I've gotten it right, then I'd go on a quick test drive to really settle the suspension. I found the test drive is essential as my initial "correct" measurements changed, and I then fine tuned to get it perfect. Hope this makes sense. Give me a holler if you feel like it as all this is still fresh in my mind

Oh, and also remember that fender wells are not perfect. What I did was got my heights "close" by measuring from floor to fenderwell, then set it "just right" by measuring from floor to the torsion bars. This is the true height/attidtude of the suspension without the variables of body panels and such.

Edward
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Last edited by edward993; 01-02-2005 at 05:32 PM..
Old 01-02-2005, 05:24 PM
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Something that may be of value is a quick refresher on the Ferch method of corner balancing. It isn't necessarily perfect, but it's a decent way to estimate corner balance without spending a fortune getting it done professionally.

Basically, the problem that you're dealing with now is that the car has four corners, each of which is adjustable in its loading. What you need to do is reduce it to a tripod, on which only 2 points are variable. The easiest way to do this is to pick up the back at a conveniently provided center-point (like say, underneath the engine), then measure and compare the front ride heights. Correct as necessary. The same goes for the back two corners -- pick up the car by a center-point at the front, then measure the rear corner heights.

Thanks to Wil Ferch for thinking this up; I've used it plenty of times with great success. BTW, each time you make an adjustment, you really have to settle the suspension by running around the block, preferably a couple of times.

Cheers,

Dan
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Old 01-02-2005, 05:55 PM
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Thanks elombard and edward993.

My initial L/R difference was 11/2" My sequence before getting the 3/4" reading was similar to yours. Bounce all four corners. Bounce the back 2 again. Took it for a 4 mile ride - parked on level ground and took the reading that yielded the 3/4". I got 5/8" and 3/4" when measuring from the outboard most point on the t-bar to the floor
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Old 01-02-2005, 05:57 PM
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I think Dan is crediting me with too much in the area of corner balance, but I do ( at least) say that any *two adjacent* wheels ( LF+LR....LF+RF.....RF+RR...or, LF+RR) ...the "total weight" of any two adjacent wheels will remain unchanged before and after corner balancing.
The (tongue-in-cheek) " Ferch-method " - -that I jokingly ask be termed this way- - is the spring plate angle calculator math that Thom Fitzpatrick kindly made so user-friendly as a plug -'n-jug program.....thanks again , Thom.

Wil
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Old 01-02-2005, 06:16 PM
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Pardon my ignorance, but I see a lot of focus on ride height which, as near as I can tell is only half the story.

My take is that ride height raises and lowers the car center of gravity (CG). The lower the CG, the better the handling due to less moment acting on the car in a turn. However, corner balance is equally important to ensure that the car wheels carry an equal load and you can predictabily transfer the weight fore and aft as you brake or accellerate.

That said, setting ride height is half the batle, since in my mind, you need to also ensure a good corner balance or the ride will not feel right.

Am I over-analyzing it?
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Old 01-02-2005, 09:10 PM
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Sorry, Wil, didn't mean to give you too much credit there. Um ... so what do we call that neat method of making a tripod out of the car? Ferch's Other Method? Whatever, it works pretty well; corner balance and ride height are intimately tied. Any discussion of ride height without corner balance is incomplete, IMHO.


Dan
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Old 01-02-2005, 09:30 PM
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Sorry Wil, but I'm going to have to give you credit as well!

Another kind soul let me in on your, um, "the other" method as described as the tripod, and that's the way I set mine. It makes sense to my pea brain since one is setting the heights of one end of the car without the other end, or its diagonal, influencing each corner. Granted, this isn't going to replace scales, but I would think it would get one really close. Has anyone done the WFTP (Wil Ferch Triangulation Protocol ) then had a corner balance? I'm curious how close it comes to the real deal.

Edward
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Old 01-02-2005, 11:37 PM
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There is indeed a diagonal cause-effect relationship that must be properly managed. The method of raising one end ( front or rear) of the car and looking at the resultant-effect on the other end is well estalished within the Porsche factory manuals. I believe there is even a little P-car specific tool...nothing more than bar stock with a center raised "ball" acting as a pivot point....that enables such a task.

HarryD....you are quite correct that getting both ride height and proper corner balance is the goal...and a difficult one to achieve without a lot of tail chasing. One minor point, however, the objective of corner weighting is not to ensure equal weighting ....but to make make sure each corner carries the proportion of weight "it should", based on where the major masses of the car already exist. For most of us ( non Brits), this will likely mean a slight left-of-center bias due to steering gear and such that is off to one side.....this is not a symmetrical Formula type car....

On the other points, thanks to my staunch supporters ( ! )...but I simply added to the larger knowledge database that already exists.....

Wil
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Old 01-03-2005, 05:46 AM
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Wil,

Thanks for the clarification. I knew that the weight distributin was not equal but but failed to state it as well.

I will be doing some suspension work this winter and will most likely try to get some of the balance done prior to taking it to my shop.
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Old 01-03-2005, 05:24 PM
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