Better Suspension for 911T 1970

[Aunt Kate]

Hello,
i have an 911T from 1970, and would like to improve the suspension for street use. The suspension is not worn out.
Original Torsion Bars-Front 19mm -Rear 23mm,
Original Sway bars- 15mm front-rear,
Turbo Tie rod kit, Bilstein HD-front-Bilstein Sport-rear.
I think the suspension setup could be better, maybe bigger Torsion bars, or bigger sway-bars? What do you think?
What was the genuine setup of the 1973 RS 2.7? I think this could be nice!
Thanks a lot!

Rainer

[Az911]

What kind of driving are you going to be doing with the car?

[Bill Verburg]

You already have the same suspension as used on the '73 RS. The only other change which was used only after the first batch of 500 was the relocation of the pivot points for the inner rear arms ala what was done on the turbos.

The pivot was moved inboard 15mm and backward 47.5mm, shorter arms are used as a result.

About the only other chage to replicate the RS is to replace the steel front crosmember w/ an aluminum one.

[Aunt Kate]

Hello Bill,
does the 73 RS realy have 15mm sway-bars, and 19-23 torsion bars?
Hello Steve,
maybe some classic-hilclimb events. (bad streets)

Thank you.
Rainer

[Bill Verburg]

does the 73 RS realy have 15mm sway-bars, and 19-23 torsion bars?

Yup

[Randy Webb]

How many pennies do you want to spend? Just give an estimate to the nearest power of ten....

Actually, your suspension is probably not the same as an RS -- yours is probably 33 years old right? That means you replace all the rubber.

And how harsh will you tolerate? Put another way: what balance of street/track will you do? Is it all street as your intial post suggests?

[JNadal]

http://www.pelicanparts.com/cgi-bin/wizards/parts_wizard.cgi?wizard_root=911_suspension_wizard

click on all of the most expensive parts!

seriously,
you said hillclimb, so youd probably need bigger torsion bars, new shocks and new bushings and maybe a camber bar.

oh, and throw in an adjustable sway bar for good measure.
if you're on a budget, Id go in this order
bushings
shocks
camber bar
torsion bars
sway bars

you definitely want the bushings and shocks to be in good condition if you start to upgrade the rest of the suspension.

[Zeke]

The shocks you have are not well matched to the stock t-bars. Up grade the t-bars (and change the bushings) to 21/26 or 27 and I bet it rides softer than it does now. Yes! And corners better as well.

Shocks are there to dampen springs (t-bars). If there is no spring to speak of relative to the stiffness of the shock, it will beat you to death. Of course, the opposite is true as well. Stiff springs and weak or underrated shocks, and the car will bounce wildly.

BTW, tire sidewall flex figures into the equation, so if you are using 70 series tires, don't try to stiffen the car like you were going to run 45's.

[911pcars]

Bill,
You might be referring to the RSR rear suspension that had relocated pivot points. The RS cars had the same suspension, geometry-wise, as other early 911s.

Assuming the suspension bushings are in good shape, I agree with Milt and also suggest 21/26 or 21/27 torsion bars along with corner balancing and 4-wheel alignment.

Sherwood

[Bill Verburg]

The shocks you have are not well matched to the stock t-bars.

I have to disagree, the Bilstein shocks were specificaly calibrated to the stock suspension and are in fact the ones originally specified for the 2.7RS(other models used Koni or Boge). If bigger bars are used then yes, by all means recalibrate them.

You might be referring to the RSR rear suspension that had relocated pivot points. The RS cars had the same suspension, geometry-wise, as other early 911s.

Again I have to disagree, according to Fr&#232re, ¹"this change, which necessitated the use of shorter inner suspension arms, was incorporated in 2.7 litre Carrera RS models after the first batch of 500 required for homologation in Group 4 had been made."

_________________
1. Paul Fr&#232re, "Porsche 911Story", 6^thEd. p160

[Grady Clay]

There is another important issue when considering struts for a ’69-’71 911.
Porsche changed the attachment method between the ball joint and the strut
from a pinch bolt (on the left) to the wedge pin (on the right) in '72.

The pinch bolt isn’t sufficiently strong and in some cases
the ball joint pin can actually pull out past the bolt.
Also, after 30 years, it may only be rust holding the ball joint pin in the strut.

I will urge you to replace the struts and ball joints.
Now is the time to do this when you are replacing tie rod ends, torsion bars, etc.
"
"
(C) 1972 Dr. Ing. h.c. F. Porsche A.G.

Doing this in conjunction with the torsion bars will give you the best results by
matching the shock characteristics to the torsion bar and sway bar sizes.

Best,
Grady

BTW, '70 and '71 914-6 and 914 have the same issue.

[Aunt Kate]

Thank you for your help.
My suspension bushings are new, corner balancing and 4-wheel alignment is done. The suspension feels a bit harsh. I think it is so as Milt means. Bilsteins are new.(Front P36-112 Rear B46-0975) Wheels are Fuchs 6x15, tires are RE71 195-65-15. Can the torsionbars be weak too? What torsionbars do you recomment.

Rainer

[Bill Verburg]

If we are going to pick nits there was also a change in upper and lower rear shock mounting position starting w/ the E series '72s. This change eliminated the previous rearward tilt of the shocks improving response to wheel movement. As aresult the length of the shock changed as well.

Rainer, the front shocks are correct but the rears are for a '73 - '89, any fitment issues?

The biggest improvemant in handling will come from fitting the correct RS 7 & 8 x15 wheels, in '73 they used 185/60x15 and 215/60x15, but today I would advocate 205/50 and 225/50 tires from the manufacturer of your choice. Of course you will need to add the correct SC/Carrera flares to do this.

[Aunt Kate]

Hello Bill,
i think the rear shocks fit perfekt. Can you tell me the difference of the shocks from 1970? I dont want to change the rear flares. Maybe 7x15 rear and 205-60-15 tires?

[Randy Webb]

Nits is what the whole concept of Pooschey ownership is based on....

AUnt - I'd look in the parts section to see if that anwers your question re the shocks. Or is that what you meant?

re the shocks - you want the whole system of springs + shocks (etc.) to not be under-damped and not be over-damped. These are terms from physics that relate to damped harmonic oscillators. You can look that up in any physics text for some diagrams if you want. The bottom line is to match the shocks or the car will "feel wierd" going over any sort of bump.

And the sway bars have to be matched to the system also....

And - finally - how old are your tires? Are you sure they are less than 5 years old?

Can you expalin what a bit harsh means? Have you tried this car vs. other 911s of the same vintage (i.e. what is the comparison to?). Remember this is not a modern suspension design and is not a family sedan.... Has anyone else (experienced 911 driver) driven or ridden in the car? Nothing personal, but we need to eliminate driver preference as a factor here - it may be that your car is just like "ought" to be.

[Bill Verburg]

Can you tell me the difference of the shocks from 1970?

The later shocks are longer and wider. If you have no interference then they must be working for you.

[911pcars]

"according to Frère, 1"this change, which necessitated the use of shorter inner suspension arms, was incorporated in 2.7 litre Carrera RS models after the first batch of 500 required for homologation in Group 4 had been made."


Bill,
Not to beat a dead horse. Mr. Frere is an acknowledged expert, but Bruce Anderson's text (p. 14, 911 Performance Handbook) implies that the above applies to 49 2.7 RS cars that were rebuilt as option 491 (that includes the 2.8 RSR engine). These and all RSRs built after had the revised rear suspension pivot points and shorter arms. With the exception of these 49 that were modified to RSR specs, RS 911s had regular 911 suspension.

The Euro 3.0 engined RS of 1974 was the basis for the Group 4 versions that were homologated for the RSR versions for that year.

Can anyone else corroborate Frere's or Anderson's version?

Sherwood

[Bill Verburg]

² Bruce Anderson, "Porsche Performance Handbook 2^nd ed." p203

[Grady Clay]

Guys,

Chill.
Porsche was experimenting with everything in those years (actually they are still doing it.) PAG looks to it’s customers to help find the “best for the specific application” race parts. It is a two-way street.

Back in the “long ago” I would call Frau Baer with a question or application, she would find the right person and give me a specific answer, if possible, the next morning. I would order the parts and a few days later they were in Denver. Porsche was very responsive to its customers.

This is where the suspension that is on rs911t, pwd72s, and many others came from. This was interactive Factory involvement.

Best,
Grady

[Aunt Kate]

re the shocks - you want the whole system of springs + shocks (etc.) to not be under-damped and not be over-damped. These are terms from physics that relate to damped harmonic oscillators. You can look that up in any physics text for some diagrams if you want. The bottom line is to match the shocks or the car will "feel wierd" going over any sort of bump.

And the sway bars have to be matched to the system also....
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Hello,
do you know a list in the www, which shows what shocks, torsionbars and swaybars will fit togeather?

My tires are three years old.

Rainer