Early 911 w/3.2 Spring Plate Angle Calculator question

[70S Targa Guy]

I have done plenty of research on this site on how to upgrade my suspension including replacing shocks, tie rods, ball joints, torsion bars, spring plates and bushings and lowering car to Euro ride height and this site has given me the knowledge and confidence to tackle all of the above without any major problems. I am getting ready to perform the final job of upgrading rear torsion bars, upgrading to adjustable spring plates with new Neatrix bushings and set ride height using the handy Will Ferch Spring Plate angle calculator and that is where my question is. First... the background of the patient:

The patient is a 1970 911S Targa with a 3.2 in the rear.
I have recently put in new front inner and outer wheel bearings and races, front strut brace, front sway bar drop link bushings, turbo tie rods, ball joints and Bilstein Sports on all 4 corners. Yesterday I removed stock front 18.8mm TB's and upgraded to 22mm front Torsion bars and set front ride height to exactly 25.25" on both front left and front right sides. The rear tosion bars in the car right now are stock 23mm with stock non adjustable spring plates with a 20 year ago upgrade to Weltmeister plastic poly bushings. The present rear ride height is Left Rear=25 1/8" and Right Rear= 25". I wanted to have the fronts done and at the proper height before I tackled the more difficult rear TB upgrade. Fronts were simple and done in about 30-40 minutes. My objective is to have front height at 25.25" and rear at 24.75" The car is riding on 4 brand new BF Goodrich G-Force Sport 4V 205/60/15 tires on original Deep Sixes. Final project after rear TB's will be bump steer kit installed that I purchased from our host already.

Here is my confusion:
I have the car on 4 jack stands and the car is perfectly level as measured by one of those magnetic angle protractors placed on both door sills. All 4 wheels are off the car but the car is totally together as I have not yet removed the lower shock bolts or any bolts on the spring plate and/or trailing arm. I measured the existing angle of the spring plates with everything together and perfectly level. Both left and right spring plate angles were exactly 25 degrees??? My dilemna is using the Spring plate calculator I inputed the following:
Weight of my 1970 911 according to Porsche is 1020 Kilos = 2248 LBS
Added my weight............................................ .........................200 LBS
Added estimated additional weight of 3.2 vs 2.2 engine.............100 LBS
Gas............................................... ............................................50 LBS
TOTAL WEIGHT INPUTED INTO CALCULATOR..........................2600 LBS
SIDENOTE:Reading Will Ferch's explanation of the calculator there is no mention of adding driver's weight or fuel. Not that it make a huge difference but should I be adding my weight and fuel weight into the total weight?

I plugged the 2600 LBS into the calculator, plugged in desired height-Euro Height (my desired ride height is actually 1/4" lower than Euro) and plugged in 27MM tosion bar with 40/60 weight distribution and the calculator gave me a spring plate angle of 25-26 degrees....the exact angle that I am getting now with the original 23mm torsion bars in it??? If I were to plug the same above data into the calculator except plugging in 23mm for the TB instead of 27mm,the calculator gives me 38-39 degrees. Am I doing something wrong here? I don't understand why the spring plate calculator gives me 25 degrees for 27mm tosion bars while my present spring plate angle with with the stock 23mm TB's is at 25 degrees and is presently almost exactly at Euro height right now at 25"

Finally, I am going to be using silicone grease on the outside surface of the outer Neatrix bushings and use the longer bolts supplied with the bump steer kit to make it easier to reinstall spring plate....Super Glue or not to Super Glue the inside surface of Neatrix Bushings to the spring plates? I have read both sides. I prefer NOT to super glue, epoxy or whatever.

Thanks in advance for any help.

[rusnak]

My own $.02 is that the Neatrix rubber is much harder and less compliant than the factory rubber. It is less likely to deform, and much more likely to separate from the radius arm because it lacks the ability to deform, which is what gives the factory spring plate such a low friction and high spring rate. I would therefore say use synthetic grease on the rubber where the radius arm and rubber meet.

You will have less trouble installing the Neatrix rubber into the body than I think you are anticipating.

[Trackrash]

You will need to disconnect the torsion arms from the rest of the suspension to get the correct reading. The stock torsion bars have a lot of "preload". In other words the torsion arms have tension on them from the shock mounts and trailing arms. You may also have to remove the bottom bolt from the spring plate as the torsion arm may also be hitting it as well. The larger torsion bars will have less preload and will actually be easier to install.
As for the bushing. I'm not sure if the inner part is supposed to have the torsion arm to slip in it. The original rubber bushings are vulcanized to the torsion arm. Of course the plastic bushings and the poly bronze slip on the inside and require lube.

[uwanna]

Originally Posted by Trackrash

You will need to disconnect the torsion arms from the rest of the suspension to get the correct reading. The stock torsion bars have a lot of "preload". In other words the torsion arms have tension on them from the shock mounts and trailing arms. You may also have to remove the bottom bolt from the spring plate as the torsion arm may also be hitting it as well. The larger torsion bars will have less preload and will actually be easier to install.
As for the bushing. I'm not sure if the inner part is supposed to have the torsion arm to slip in it. The original rubber bushings are vulcanized to the torsion arm. Of course the plastic bushings and the poly bronze slip on the inside.

As Trackrash said, you need to take off the shocks, remove spring plates from the swing arms, and also the lower rearmost springplate retainer bolt to be able to measure the springplate angle while the springplates "hang" there free. I would suggest you get a copy of the Bentley manual and Wayne's 101 Projects manual. Both books outline the procedure. Also, scribe the location of the springplate onto the swingarm so you can get your alignment back where it was, before you took it apart.

[70S Targa Guy]

Thanks for the replies. I wasn't sure but my hunch was having all the spring plate bolts and bottom shock bolt still attached had something to so with not getting the true angle. Thanks for confirming my hunches. I will be using silicone grease instead of super glue on the Neatrix bushings where they are in contact with the radius arms. Somewhere I do have the original burgandy Porsche 3 ring two volume Factory Manuals buried in one of my many boxes in storage..perhaps this is a good time to track it down as a reference for this job.