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Spec 944, torsion bars, conversions Oh My!

 
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JamesWilson  



Joined: 10 Jun 2005
Posts: 132
Location: San Diego, CA

PostPosted: Thu Jul 21, 2005 2:23 am    Post subject: Spec 944, torsion bars, conversions Oh My! Reply with quote

Trying to get the 931 suspension set up for PCA autocrossing. The Spec944 guys are running 400# springs in the front with either Konis or Bilsteins with camber plates and the Weltmeister sway bar. In the rear, they typically run 30mm torsion bars and the adjustable rear bar as well, dialing in more bar for the autocross but otherwise leaving everything the same as their track setups on our long sweeping courses in San Diego.

In my crossover SCCA autocross class, I am allowed to change attachement points of the suspension pieces. I know the rear coilover conversion is popular and remove the rear torsion bars, but what rates would be run on the coilover to mimick a 30mm t-bar?

FWIW, we're probably just going to go with 300 or 350 in the front (the 250's that are on there now are waaay to soft), stock t-bars right now but awaiting the conversion when the Bilstein Motorsports struts and camber plates arrive.

-JW
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924RACR  



Joined: 29 Jul 2001
Posts: 8320
Location: Royal Oak, MI, USA

PostPosted: Thu Jul 21, 2005 3:31 am    Post subject: Reply with quote

On the Paragon site in the Tech Section, they have equivalent rates for coilovers and t-bars...
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Vaughan Scott
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jjadczak  



Joined: 03 Jan 2003
Posts: 346
Location: Accokeek, MD

PostPosted: Fri Jul 22, 2005 4:23 am    Post subject: Reply with quote

That's what we have on our 924's that we race: 400# front springs, Koni's (Yellow) 30MM torsion bars. The weakest link is the plastic and rubber bushings we have on the suspension and thr Koni's should be Bilstein's. We eventually need to replace this.

I think it's really fun and that's what some of the 944 Cup racers are running this set up. Other people I know go even stiffer that that but since I've never tried this, I can't comment on this.

I do wish that we could have coil-overs in the rear. That's not SCCA IT legal. It's a lot better than running torsion bars.
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Jeremy "I'm Faster than My Dad" Jadczak
#53 Porsche 924 (sold '06)
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924RACR  



Joined: 29 Jul 2001
Posts: 8320
Location: Royal Oak, MI, USA

PostPosted: Fri Jul 22, 2005 4:45 am    Post subject: Reply with quote

The 30mm/400#/Bilstein setup is indeed what I'm running too, and seems like a perfectly good starting point. I'm still waiting for stiffer parts to arrive...
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Vaughan Scott
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john h  



Joined: 06 Nov 2002
Posts: 827
Location: Wellington New Zealand

PostPosted: Thu Aug 04, 2005 3:38 pm    Post subject: Reply with quote

At the front I run 300lb springs 3 1/5 degrees negative camber and slight toe in with 25 mm front sway bar 7 inch rims.

At the rear 27mm torsion bars 18 mm adjustable sway bar. 8 inch rims with 21 mm spacer, zero toe, 3/4degrees negative camber. Back of car is also set up to be 25mm lower than the front - Looking side ways on it appears as if the rear suspension has collapsed.

But does it go round corners, sits flat , can do last minute braking with very little weight transfer to the front hence no front brake lock ups. Despite the rear down attitude it is still stable in a straight line and a max revs in 5th it's still rock solid with no front end lift. (GT spoiler and front splitter helps with this)
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JamesWilson  



Joined: 10 Jun 2005
Posts: 132
Location: San Diego, CA

PostPosted: Thu Aug 04, 2005 4:13 pm    Post subject: Reply with quote

We are currently weighing in the cost-vs-necessity (for now) factor on choosing a front camber plate. The Paragon Products piece is around $300, while the Weltmeister piece runs a spicy $700.

The upper mounts NEED to be replaced anyway, but the last opeion is to run the KLA Industries solid billet upper mounts (non-adjustable) and spherical bearing. At $114 per set retail, that's an easier pill to swallow, and we may even be able to modify the assemblies to get a little negative camber out of them.

I think we are going with the KLA pieces to match with the new custom-valved Bilsteins (God I love living LESS THAN 2 MILES from Bilstein Motorsports here in CA), toying with rear spring rates depending on our tire choice for the remainder of the season.

Comments?

-JamesW
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924RACR  



Joined: 29 Jul 2001
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Location: Royal Oak, MI, USA

PostPosted: Thu Aug 04, 2005 9:57 pm    Post subject: Reply with quote

Sounds good... added camber and caster adjustment from the Paragon units is nice, no question, but the KLA should do you fine for now...
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Vaughan Scott
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