Rear Torsion Bar setting question
 

OK I am mentaly going thru the motions of putting new torsion bars in the rear, I read the manual and came up with a question I dont know anything about.

In the book it says to set the inclination angle to 32 degrees for a Carrera with 25 mm rods (86') and 34 degrees with a 26 mm rod in a turbo....

(if I read that right)

SO - is the angle change due to weight, ride height, stiffer bars or what? (guessing weight)

THEN - how it effects me, I am putting 30mm rods in... should I comp the angle? and if so.....how much? and which way? (less angle because the rods are stiffer, to maintain aprox same ride height)

-starting from stock-

Thanks for any info, its an exciting job but one I hope not to screw up and also minimize down time

Look up Wil Ferch's spring plate angle calculator.

Here: 911 Spring Plate Angle Calculator

1. The initial angle is a combination of weight of the car and spring rate (stiffness) of the torsion bars.

2. The calculator at 911 Spring Plate Angle Calculator will get you close, but you will probably have to make small adjustments to get the ride heights correct.

AWESOME!!

THANKS!@

so as far as small ajustments, you are not talking about removing the torsion bars, but rather adjusting the ecentric right??

LOVE THIS INFO!

Either works for small adjustments. I remove the bars and re-index. I think you need special wrenches to use the eccentrics.

Ivangene,

Knock yourself out reading all the posts on torsion bar removal/indexing ... lol
I replaced mine last Summer,wasn't all that bad !

Get yourself a small digital level ( Craftsman )and you will also need the special thin wrench for the eccentric nut adjustment/removal.
Easiest way i found was to jack your car evenly on all fours and aim for 0 degrees while measuring at your door sills,then when you loosen up your rear arms and hang down your spring plates you take a base measure with the level before you remove your existing bars , then when you install your new bars you aim for the same degree on your spring plates, or if you want to lower your car you just aim for a lesser angle...
Good time to install new ER hard rubber spring plate bushings as well,while you're there !

Try to leave your eccentric in a neutral position when you install and index your new bars,that way if you ever do a corner balance later on you will have some room for adjustment !
I spent a whole day fiddling around and reindexing over and over for a 1/4 inch with the right rear without using the eccentric ...
Well,that's just me :)

Have fun !

Cheers !
Phil

The calculator is surprisingly spot-on, and with such big bars you should gave no trouble adjusting ride height with the eccentrics.

Good advice to set the rear spring plates in the "center" position as you re-insert to whatever angle is deemed proper. The "center" position allows a small amount of up/down adjustment without having to re-index the bars.

FWIW....from the factory.....the plate is NOT set in the centered position, but instead is hard-against the stops to only allow *raising* the car. The factory figured the bars sag/age with time, and you might end up too low and may want to scoootch it up a bit.

Thanks Wil, great tool I feel very informed and confident that I can do this.... now if I could just pick a bushing and feel confident it wont pinch and bind when bolted up....(and doesnt break the bank)

A good bushing is the Netix ones, simple and cheap.

Thanks James, I have been on the fence about bushings... almost pulled the trigger 3 times on the Netrix.. ended up on the Poly-Graphite but I plan to turn the OD/ID to match the parts with no binding (aka squeak) - I have a Hardinge Toolroom lathe :p

So a Q for Wil (or others) - on the calculator there are ride heights and I dont understand them. Is there a place to figure which I want (looking for "1-2 fingers of fender clearance on 245/45 16's)

Thanks guys for "holding my hand" as I walk thru this unknown territory, Hope to be able to help someone out as much someday too !

Ivangene,

I think i still have the degrees written on my spring plates when i did the whole torsion bar/bushing/lowering schmeel last Summer...
That was with the car leveled and measuring at 0 degrees at both door sills.
One finger gap rear wheel clearance !
It would be a good baseline to start off ...

Cheers !
Phil

I think you are asking the 3.8" static ride height number asked by the calculator.....this is the measurement of 2 reference points that bring you to "Euro" ride height....the most normal target for most people. My collaborator Thom Fitzpatrick ( "widebody911")....if I recall correctly... revised the software a bit later on...and it allows entering some target numbers higher and lower than 3.8" that will translate directly to same-amount higher or lower ride height settings.

Netrix for those searching