Why did my car rise up more than an 1"

[eurocarrera]

I've seen several posts about this already, but there seems to be no definative answer. I just recently did the following to my car (and let me tell you I saved a bundle - thanks to the notes that I have read from everyone here - thank you, thank you!):

1985 Carrera
* 22 MM front and 28 MM Rear torsion bars
* Bilstein Sports on all 4 corners
* Turbo Tie rod kit
* New ball joints
* Poly busings in front (left the rubber ones in the rear per Wayne's advice)
* New brake pads
*Wheel bearings (front)
* Steering wheel bushing - repair
* Lowered to 25 3/4" front, and 25 1/2" in the back
* 4 wheel alignment

Since I marked everything correctly in the front and rear before I took everything apart, I can only guess that the ride height had to do with the fact that my old stock torsion bars (probably from 1984) were just sagging. I mean the rear end of the car shot up over two inches alone after placing the torsion bars back into the exact same place they were before. I had to reindex them up one notch to put the car back to the appropriate height. So a few questions:

1. Is the ride increase the torsion bar being worn, the Sport shocks, or am I missing something. Yes, it appears that the sport shocks do have a lot of pressure on them and will return very firmly to the extended position, but do they have that much pressure?

2. If I lower the front another 1/2", I know that will mess up my alignment via changing the tie rod dimensions, but if I lower the rear by adjusting the large index nuts nearest the tosion bar, will that mess up the alignment?

3. What would I expect to pay for a torsion plate adjustment to lower the car more (in California), or how much is one of those thin wrenches for doing it yourself, and where can you get one?


Thanks!

[Early_S_Man]

Bill,

You didn't say what shocks and struts were on the car previously. If the Bilsteins replaced conventional hydraulic or low-pressure gas units, or leaking Bilsteins ... it is typical to see an increase in ride height, because the bilstein internal gas pressure acts like a 75 lb - 100 lb spring rate addition! This phenomenon has been discussed in Road & Track for at least 30 years!

[Vipergrün]

Check out this handy utility to calculate the correct angles for setting the spring plates for different t-bars;

http://vintagebus.com/cgi-bin/spring.cgi

You can purchase a thin 36mm wrench at your local bike shop for about 15.00 or so. You'll also need a thin 24mm wrench to get on the other bolt. BTW, the adjusting the eccentric bolt wil only give you approx 3/4 inch higher/lower. You'll have to remove the spring plates and re-index them on the t-bars.

You should always plan on an alignment after doing suspension work like this.

[widebody911]

Did you remove that big washer from the tops of the front struts?

[Wil Ferch]

Ahhh....let's review this.....

Not only would the car raise because you have hi-pressure gas shocks ( compared to hydraulic Boges...you didn't say)...but also the original Torsion bars were 24.1 mm diameter in the rear....now you're running 28 mm... a big difference. Lining up all your previous marks would be useless in getting back to where you were. I calculated a method to *predict* the new free-hanging angle of the rear spring plate that you would need to target...once you figure-in the target ride height and new TB diameter size. It's not straight-forward...people have been doing this for 30 years and always have said it might take 2-5 tries to get it right. I couldn't believe this is the case, so I worked up the long math of what's involved.... and Thom Fitzpatrick took this basis and worked up a software package that does the hard math quickly and easily. Search the archives and let us know if you can't find it.

--- Wil Ferch

[ChrisBennet]

Originally posted by Wil Ferch
Ahhh....let's review this.....

Not only would the car raise because you have hi-pressure gas shocks ( compared to hydraulic Boges...you didn't say)...but also the original Torsion bars were 24.1 mm diameter in the rear....now you're running 28 mm... a big difference. Lining up all your previous marks would be useless in getting back to where you were. I calculated a method to *predict* the new free-hanging angle of the rear spring plate that you would need to target...once you figure-in the target ride height and new TB diameter size. It's not straight-forward...people have been doing this for 30 years and always have said it might take 2-5 tries to get it right. I couldn't believe this is the case, so I worked up the long math of what's involved.... and Thom Fitzpatrick took this basis and worked up a software package that does the hard math quickly and easily. Search the archives and let us know if you can't find it.

--- Wil Ferch

Of course all the math goes out the window when you switch to gas shocks...
-Chris

[eurocarrera]

Warren, I originally had stock HD shocks on all four corners, and the stock torsion bars ( which were really small).

Thom, since this was originally a European car (not intended for the US), I don't think it ever had the washers - I checked anyway just to make sure, and they weren't there.

Thanks for the feedback guys - I may stop by the bike shop later tonight!

[Wil Ferch]

HI:
Chris points out that the math to rest torsion bars goes out the window when you add the complication of gas shocks on top of the TB bar size change.....

Nor entirely correct.....

If you follow my formula..you'l get real close, and the Tech Spec books that Porsche used to offer ( as well as the factory manuals), identify the the free-hanging angle change necessary when setiing up for gas vs regular shocks. The difference is set up is usually one ( 1) degree difference. Angle is measured as drop from horizontal:

For example ( these are only sample numbers, do the math for your actual case)
- regular car with hydraulic shocks and 24 mm TB's... 35 degrees
- regular car with gas shocks and 24 mm TB's ...34 degrees
- Ferch/ Fitzpatrick method for 28mm bars. ....24 degrees
- Ferch/Fitzpatrick method...correct for gas shocks, too..23 degrees.

---Wil Ferch

[eurocarrera]

How exactly would the alignment change in the rear? I understand that in the front it would change the tie rod adjustments, but what would it affect if I lowered the car another 1/2" in the rear?

Thanks!