Need help with spring plate angle and lowering

[kavadarci]

Hi,
With help from a fellow member I’m tackling lowering f of the back as it sits at massive 27.5 inches from the ground or 15.5 inches from the Center of the hub to the wheel arch.

My spring plate angle is 30 degrees when discontented from the banana armsitting unrestricted but connected to the torsion bar.
I want to lower 4 inches for start.
What is the angle I should be looking for on the plates to achieve this height?

I don’t have adjustable spring plates.

[tirwin]

Here is a calculator:

https://www.elephantracing.com/tech-topics/spring-plate-angle-calculator/

The old one seems defunct but thankfully I found that Chuck has one on his website now.

[kavadarci]

Thank you,
What is the factory torsion bar for 1976 911 targa? I'll find the weight online.

[tirwin]

I found this post this that says it’s 23mm.

http://forums.pelicanparts.com/porsche-911-technical-forum/220740-torsion-bar-sizes.html#post1906706

[BK911]

The end of the spring plates moves about half as much as the end of the trailing arm.
So for a 4" ride height change, 're index the torsion bar until the end of the spring plates moves 2".
That will get you really close.

[brianlay]

You don't really need a calculator.

according to the factory 0 degrees 50 seconds changes the ride height 6.5 mm (0.256 in.)

That's the smallest change you can make with the older style torsion bars.

4 inches divided by 0.256 equals 15.625

15.625 X 50 seconds equals 13.02 degrees, so your new angle should be approx. 17 degrees

[brianlay]

Pre-Carrera torsion bars had 40/44 splines

[bkreigsr]

Originally Posted by brianlay

You don't really need a calculator.
according to the factory 0 degrees 50 seconds changes the ride height 6.5 mm (0.256 in.)
That's the smallest change you can make with the older style torsion bars.
4 inches divided by 0.256 equals 15.625
15.625 X 50 seconds equals 13.02 degrees, so your new angle should be approx. 17 degrees

Something is amiss here. A 17 degree angle (unloaded at the plate) is going to put your rear in the weeds, and the exhaust is going to start a fire.
My magic number, with a full tank, came in at 31.6 degrees with the fender lip sitting at 24.25 inches. (5.5x14" Fuchs - so YMMV)
Bill K

[kavadarci]

My cutr by angle is 30 and the car is too high, alone degree will not change much.
But then going to 17 degrees that will raise more.

Hmmmm

[kavadarci]

Originally Posted by BK911

The end of the spring plates moves about half as much as the end of the trailing arm.
So for a 4" ride height change, 're index the torsion bar until the end of the spring plates moves 2".
That will get you really close.

How can I move the spring plate when it’s under pressure from the torsion bars?

[brianlay]

17 degrees in the lowering direction
I couldn't tell from your photo which end was up!

[Driven97]

Originally Posted by kavadarci

How can I move the spring plate when it’s under pressure from the torsion bars?

You have to pull out the spring plate, rotate it, and key it back into the torsion bar at the lower angle.

[Evans, Marv]

Moving the torsion bar & spring plate is a real pain in the butt. You have to be able to have the spring plate come off really easily. If it doesn't, you have to pull the assembly out enough to get vise grips onto the torsion bar (padded with rubber sheet or something similar so not to scratch) to hold it & tap or pull the spring plate off the torsion bar. If you have to do that, clean the splines on the torsion bar, inside the torsion tube, & inside the spring plate & lube them up. I use antisieze. Then start from ground zero. If you're lucky enough to be able to move the torsion bar in the torsion tube & inside the spring plate splines, you have to do it by feel. Move the bar out to the end of the splines in the torsion tube until you feel it just disengage the teeth. The you can rotate it one way or the other & reengage the teeth. The you have to do the same with the spring plate. Most of the time, you'll screw that up & still have to begin at ground zero, but practice helps. Your '76 should have 23 mm bars if they're stock. I've found the calculator seems to always make the car too high. Just as an off hand guess, I'd set your angle at 27 degrees, see how it is, & go from there. Good luck, it's always one of those jobs you have to repeat several times to get it right. Just roll up your sleeves & keep at it. I was in the process of reindexing mine for about the third time (over the years), but a friend convinced me to change over to coil overs. So that's the way I'm going now. Supposedly better ride, handling, & ease if setting ride height.

[fanaudical]

Kavadarci - be sure to measure spring plate angle with the lower rear bolt and spacer removed from the spring place cover. Remove the spring plate cover completely to move the spring plate.

[Rodsrsr]

you can move the T-bar a click in one direction and move the cover a click in the opposite direction for smaller increments. btw, lowering 4" sounds like a lot. 24 1/2" is pretty low in the rear and that would only be 3" from where you currently are. Heres my car at 24 1/2 rear and just slightly over 25" front.

[donporfi]

From where you are now (30) the protractor should be at 13, meaning the spring plate must go up. But as Rodsrsr said that could be too low.
Why not try with 10 degrees, protractor at 20.

[kavadarci]

Great car, thank you everyone for the fantastic suggestions and help.

Ok, did what I had to do and set it to 17 degrees. I think this height might be ok, next turn on the spline on the torsion bar puts on 10 degrees and that might be too low.

I ended up pulling the plate with the torsion bar and I saw no way to remove that without major work so I left things as is until next time. Rubber bushings were not too bad, new ones would be nicer.

In the process little blood was shed but I think the height is reasonable now.

Let’s start with before height for reference.

[kavadarci]

Also, since i just did this, when someone does alignment and sets the camber and toe do they have to loosen the two bolt holding the spring plates to the banana arm or those never get touched?

Thank you.