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Suspension Upgrades After Mods?

I have an 84 930 with the following modifications which have all been done as upgrades when other componets failed or not proper for the car like the 7 & 8 BBS RS wheels.

G50 transmission
K27-11 turbo
Exhaust manufacturer is unknown 3"ish striaght of the turbo
Lindsey Racing 17x8 with 225-45-17 front and 17x11 315-35-17 rear
front is lowered all but one notch and rear is only lowered one notch

With the G50 my car seems to always be under load and boost is always available. I know this sounds like fun, but there is a problem. After boost is about ut .5 bar the car starts to squat down pretty hard and I am rubbing slightly on the inner quarter/lip. I love the stance of the car and to be honest would lower it more if I could.

I am curious with all of the modded 930's out there what seems to be the most effective way of curbing this issue? I am looking into upgrading the torsion bars front and rear or adding a coil over type "helper" spring set up in the back.

Per the rules here is a photo of the car moments after breaking down this last weekend during a PCA drive the ball portion of the throttle snapped off and left me without throttle just as I was starting to pull on the GSXR heading down the freeway.



Last edited by cdill; 06-13-2013 at 04:28 PM..
Old 05-29-2013, 12:00 PM
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Big torsion bars, firmer shocks, possibly raise spindles if going really low. or a lot more if ya go fully adjustable coilovers.

elephant racing / rebel racing has good stuff, TONS of threads about this stuff.

Literally TONS of threads. search a bit.
Old 05-29-2013, 12:32 PM
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Beautiful looking project you got there! I was encountering the same problem of having the rear end squat down under heavy engine load once my project starting making some serious HP. Being so, Bisimoto Engineering got together with the engineers at Eibach to develop a set of rear coilover to give further support and improved handling characteristics for the 911 chassis. What really sets this kit aside from others on the market is the inverted design to reduce unsprung weight and also acts as a limiting device when the vehicle is suspended, to protect and preserve CV/Axle longevity. I will PM you further information.


Here is an undershot picture of the project:


Old 05-31-2013, 04:37 PM
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Prrrrreeeettttycool!
Old 05-31-2013, 06:32 PM
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same problem

I have a modded 930, and I am putting down about 500 lbs. of torque. I have the same problem as you do with the inside rub. I have 30mm torsion bars and I am going to install coilovers with 400 lbs. springs in an effort to cure this squatting.
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Old 05-31-2013, 07:26 PM
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I am running 800# springs in my build to avoid this. Other options are relocating the trailing arm mounts, but this will require some fabrication.

Who did the G50 swap and do you have the torsion tube notched?
Old 05-31-2013, 08:06 PM
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One of the reasons I chose a 10.5" wheel over an 11" is to avoid rubbing in the rear under load and also to have my car at the desired ride height.

I am also running coilovers on my car which was a summer project from 2 years ago.

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Old 06-01-2013, 02:43 AM
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Rebel Racing coil over helper springs and be done with it.
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Old 06-01-2013, 08:38 AM
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Did you guys reinforced the shock towers before installing the coilovers?

And,

Did you keep the TBs installed as a combo deal, or removed them to let the coilovers do their thing on their own?
Old 06-01-2013, 08:50 AM
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Thanks to those who have replied without saying "just do a search" and sent PM's. After searching and getting some response I am planning on installing a helper spring set up and doing additional upgrades as needed.

G50 swap was done by Chris Cervelli. Not sure on the torsion tube the swap was done as part of the purchase of the car and the PO did all the work with Chris.

Slow and Rusty. I think your car looks awfully familiar to me. Did you drive it to Bishops Castle a few years back?? This is my 993 from back then on the way back.

Old 06-01-2013, 01:56 PM
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Quote:
Originally Posted by Miguel Antonett View Post
Did you guys reinforced the shock towers before installing the coilovers?

And,

Did you keep the TBs installed as a combo deal, or removed them to let the coilovers do their thing on their own?

I run 28 mm t-bars with 500 lb helpers. I also installed the RSR type shock tower gussets but you really dont need them unless you go full coil-over.
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Old 06-01-2013, 02:45 PM
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personally i never understood the concept of running "helper springs".

Let me rephrase that. Isn't running helper springs defeating the purpose. If you are going to add a rear coil over, why not just get the rate you need and eliminate the TB. If you keep the TB and add a spring, you are adding weight. Going with a straight coil over or a bigger TB would be better IMHO.
Old 06-01-2013, 04:08 PM
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Quote:
Originally Posted by Miguel Antonett View Post
Did you guys reinforced the shock towers before installing the coilovers?

And,

Did you keep the TBs installed as a combo deal, or removed them to let the coilovers do their thing on their own?
I did not reinforce my shock towers when I converted my car to coilovers.

Initially, I did run the TBs with the coilovers for a few weeks and then completely removed the the TBs.

Quote:
Originally Posted by cdill View Post


Slow and Rusty. I think your car looks awfully familiar to me. Did you drive it to Bishops Castle a few years back?? This is my 993 from back then on the way back.

Yes that was me...the year was 2008. I took lots of pictures on that day but now sadly lost due to a compute crash.

Yasin
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Old 06-01-2013, 05:27 PM
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This might help:
Helper springs are designed to completely compress at normal ride height, and used to maintain load on the main spring at full travel. Once the helper spring is closed it is inactive.

Tender springs are part of a dual rate spring system. The tender spring is open at normal load, and therefore it is still active, and closes at a predetermined load.

and:
Helper and tender springs are both made from a flat wire spring that are designed to completely compress. In Whiteline's view, the difference is mainly in the application of the spring and at what point they close in the chosen application. This is obviously dependent on spring load, where a helper spring is generally known to close BEFORE normal load is applied, and a tender spring is generally known to close AFTER normal load is applied.

Here's a link to the Paragon site showing coil over spring rate vs effective rate, and torsion bar spring rate vs effective rate. https://www.*****************.com/kb_results.asp?ID=58

If I understand this correctly, and not saying I do. A 28mm torsion bar has a 254 lb/in effective rate which is the same as a 450 lb coil over which has an effective rate of 253 lb/in.

By adding a 500 lb spring to a 28mm torsion bar is the same as using a 950 lb spring?

It seems an ideal set up would be a main/tender spring (or torsion bar/tender spring) set up. The main spring or torsion bar deals with the normal load, i.e. a good ride and handling, and the tender spring deals with the turbo squat.

Maybe some knowledgeable suspension person will pipe in and shed some light on this.
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Old 06-02-2013, 07:09 AM
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I run 22 & 29 TBs with adjust Konis, 17x9 with 255 & 17X11 with 315s with no rub at all. Recognizing that my car is not part of the over 300hp club.
However, if you guys rub - assuming proper wheels spacing & tire size - your suspension travel is "streched" somehow, because our cars - flairs - are designed to match the suspension travel - max squat - with the required fender clearance.
Old 06-02-2013, 11:25 AM
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I said 500 lb helper coil overs by mistake but they are only 150lb with 28 mm T-bars.
The helpers completely eliminated the rear squat. Wheels are 11" wide with a 315/35 tire.
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Old 06-02-2013, 01:58 PM
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That sounds better. How did you set up helper springs? Are they snug between the lock rings?
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Old 06-02-2013, 02:04 PM
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Quote:
Originally Posted by gumba View Post
That sounds better. How did you set up helper springs? Are they snug between the lock rings?

Rebel Racing offers a complete kit specifically for the early 911.

Suspension1


There is adjustability, and I have them set with no compression until the rear end would want to squat. If that's what your asking. Zero squat, zero tire rubbing.... trackion/hooking up...
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Old 06-02-2013, 04:11 PM
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So there's free play between the spring and the lock rings until the back squats a couple inches? I'm already running adjustable rear shocks with 28mm torsion bars with no tire rubbing. Just trying to get some clarification.
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Old 06-02-2013, 04:36 PM
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Quote:
Originally Posted by Rodsrsr View Post
Rebel Racing offers a complete kit specifically for the early 911.

Suspension1


There is adjustability, and I have them set with no compression until the rear end would want to squat. If that's what your asking. Zero squat, zero tire rubbing.... trackion/hooking up...
Wow thats a nice set up.

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Old 06-02-2013, 04:50 PM
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