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Bulldog9's Avatar
 
Join Date: Jan 2011
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As others have said, you need to look at front and rear adjustments together. Elephant Racing and Rebel Racing are both sites with tons of parts and information. If it's just looks you are interested in, then you need to focus on how to lower. Lots of information on that. As others have said, the front adjustment is easy. The Rebel Racing bushings make rear adjustment of height relatively simple, and they also sell adjustable spring plates.

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Old 03-21-2016, 03:36 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
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You increase the rear spring rate, you increase the tendency to spin the car on throttle lift...

Think this through. What you say you want is not what you will get.
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Old 03-22-2016, 02:03 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #22 (permalink)
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Quote:
Originally Posted by unclebilly View Post
You increase the rear spring rate, you increase the tendency to spin the car on throttle lift...

Think this through. What you say you want is not what you will get.
While not untrue, that is a very general statement. Don't forget there is a fair amount of dynamic toe change with the 911 as the rear suspension goes through it's motion. Bill V has a chart. What that gives you is passive rear steer in droop. So, if you've got soft torsions, you get more toe change, stiffer torsions, less. This definitely affects what the car does when you lift off throttle.

And since that is a transitional thing, shock damping, particularly low speed rear rebound, comes into play. Too much rebound, and the tire won't follow the surface well. Too little, and the rear mass will pop up uncontrolled and shock the tire at the peak of the force. Either will add oversteer on lift throttle, but in different ways.

Yes, rear spring rate will affect your tire loads mid corner, but dynamically there is a lot more going on. Again, part of why you need to treat the whole suspension as a system.

This is just my opinion, but I think that 30+ years of tire tech advancement has pushed grip levels beyond the limits of factory suspension. A little updating puts the total suspension deflection back closer to the intended amounts.
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Old 03-22-2016, 04:58 AM
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I am going full coil-over on my 951 DE/street.

I am working with Steve Weiner at RennSport Systems on my 930 build. will do some serious suspension upgrades as this clone was done with full wide body slantnose and mod'ed 3.3 turbo motor ~450HP, but left stock SC suspension / brakes.

building the 930 for DE/street but will retain torsion bars as going coil-over on the rear of an older 911 needs a lot of reinforcing. interesting you have to drop the whole torsion tube to remove the torsion bars on the 951....

on my 85 911, I upgraded torsion bars, 22/29mm, and koni adjustable shocks during the time I used for DE/street. did not upgrade bushings on it, was considering that as next move but decided to retire from DE and reverted to street. now have the 951 for DE.

as noted, you need to think through what you want for results and it needs to be a "balanced and coherent system" to achieve the best, most satisfying results.

good luck.

951 suspension for visual interest and the gaping space with the torsion tube dropped on it.





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Old 03-22-2016, 07:45 AM
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Hi PWICK911

Researching this forum is your best bet, so you can make up your mind based on other projects.

My suspension upgrade was based on one premise: balance

Suspension needs to be balanced against your tires, you budget, your driving plans and personal taste. It's difficult to ask a diverse group what's best, especially when you're only talking about the back half of your 911. It's like asking us what's the best look for half a woman you'd like to date...a lot of personal preference and of course, you never date only half of a woman. It all adds up.

If you'd like to explore my suspension build thread, you may find some useful info:
'78 SC Elephant Racing Suspension Rebuild

Cheers,

- Craig_D
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Old 03-22-2016, 11:39 AM
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Quote:
Originally Posted by Craig_D View Post
It's like asking us what's the best look for half a woman you'd like to date...a lot of personal preference and of course, you never date only half of a woman. It all adds up.
Great summation.
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Old 03-22-2016, 11:54 AM
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Quote:
Originally Posted by Craig_D View Post
Hi PWICK911

Researching this forum is your best bet, so you can make up your mind based on other projects.

My suspension upgrade was based on one premise: balance

Suspension needs to be balanced against your tires, you budget, your driving plans and personal taste. It's difficult to ask a diverse group what's best, especially when you're only talking about the back half of your 911. It's like asking us what's the best look for half a woman you'd like to date...a lot of personal preference and of course, you never date only half of a woman. It all adds up.

If you'd like to explore my suspension build thread, you may find some useful info:
'78 SC Elephant Racing Suspension Rebuild

Cheers,

- Craig_D

Thanks Craig I will read with interest.
Old 03-22-2016, 01:01 PM
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Just wanted to let everyone know that we also just updated our performance section that you can check out for some performance/suspension upgrades HERE. Check it out.
Old 04-19-2016, 03:26 PM
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Quote:
Originally Posted by Driven97 View Post
Some? Here's a factory adjustable rear spring plate (what you should have on your car):


...
Hi.

Can anyone tell me the difference in ride height from maximum to minimum angle?
And perhaps also how many degrees between?

Einar

Last edited by Einar Irgens; 05-17-2020 at 10:45 PM..
Old 05-17-2020, 09:15 AM
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Quote:
Originally Posted by PWICK911 View Post
Looking to upgrade the rear suspension on my 911sc

Anti roll bar
Drop links
And lower it 20mm

Currently have green bilsteins which I will keep.

What do I need, and has anyone done something similar.

How much adjustment is there in the rear arms?

Thanks
Define "upgrade"

how will the car be driven??
Old 05-17-2020, 11:36 AM
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You may want to be aware of just making the rear stiffer. It will throw off your handling, making your car want to over-steer.

If you are keeping the torsion bars stock, then also upgrade the front sway. I would strongly recommend an adjustable front sway bar to match the upgrade in the rear.

To answer your first question. It is impossible to know where your current adjustment is on the rear torsion arms. It very well may be already as low as possible. Meaning you will have to re-index your torsion bars.
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Last edited by Trackrash; 05-17-2020 at 12:54 PM..
Old 05-17-2020, 12:51 PM
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I just did all of this work on my '78 SC. It's expensive and a VERY slippery slope. Well worth it for the drive, maybe not wise from an investment point of view. (having more in the car than you wanted)

That said, I did rebuild the steering box, re-plated everything possible, powder coated all the black bits, tumbled the aluminum stuff: rear swing arms, front hubs and cross bar, new alloy brakes up front, new bearings, seals, bushings, ball joints, turbo tie rods, rotors, brake pads, alignment, corner balance. EVERYTHING. Plus new clutch parts, new flywheel, E-brake cables, clutch cable. Dang, slippery slope of "while you're in there."


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Old 05-17-2020, 01:53 PM
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Beware the slippery slope......

Hi PWICK,
It has been said that the factory set the rear spring plates for Increasing the rear height to compensate for rear settling. This means that you may not have any adjustment available to lower the car unless the rear suspension has been worked on AND someone indexed the rear bars so that the adjusters were set at “mid point” AND that the PO had the car corner balanced and aligned AND there is some adjustment left to lower the car. Short answer, probably not without reindexing the bars.
Do you know if the suspension bushings have been replaced??? If not, it is probably time to do them. In the process of replacing the rubber, you have the choice of original stiffness, or sport stiffness, (assuming mostly street use, which rules out poly bronze, polyurethane, or monoballs).
Additionally, you are likely to find some abrasion of the front T bars, due to wear/sagging, which leads to the previously cited recommendation to increase the size of the T bars.

Importantly, most suspension work will require re-establishment of ride height and realignment, which has a significant cost that if you plan thing out well, you only have to do once.

This suggests that you talk to an experienced pro that has, or can recommend a balanced package to hit your goals. I don’t have much Porsche suspension experience, but have been well served by Chuck At Elephant, both in understanding my desires and recommending suitable components, followed by good service.

Moving on - way down the slippery slope,, while you are in there:
Ball joints, blast and powder coat the parts, or plate them,
Steering rack overhaul, mastercylinder, wheel bearings, caliper overhaul, discs, pads,
Spring plates with more/easier adjustability, adjustable anti-roll bars to tune the handling.

The list is dependent on “need” and desires, then do the corner balance and align.

Hope you don’t find any serious ancillary issues/RUST.

Good luck,
chris

Old 05-17-2020, 03:38 PM
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