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What Are the Suspension Setups SP2 Racers Are Running?

 
Old 06-14-2019, 07:38 PM
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T&T Racing
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Default What Are the Suspension Setups SP2 Racers Are Running?

Hi Dave,
I am starting this thread because I was reviewing a Rennlist Posting on 944 Front Springs started in 06.07.2005 by OP Bill L. Seifert. The conclusion from the 3 pages of threads that there was no consensus.

I have a 1983 Porsche 944 setup for SP2 but the car is raced in SVRA. The bottom line is the car has too much understeer and specifically to Lime Rock is where the testing was done.

The original suspension setup was front spring 450#/in, Target front sway bar, Koni double adjustable shocks, and reinforced gusset steel lower control arms, and polyurethane suspension bushings, Ground Control camber/caster mounting plates; and the rear has 31 mm hollow tube torsion bar, Koni double adjustable shocks, 951 trailing arms,Tarett rear sway bar, bronze bushings and rigid mounts for the torsion bar housing and attachments. The car had 7x15 square R6 tires/wheels. The front camber was -3.0, castor +3, and toe was 0. Rear was standard setup. The car had too much understeer.

I determined the Target sway bars had only one adjustment setting where 100% of the rotation force was perpendicular to the front or rear lower control arm. Any other setting had both a perpendicular and horizontal force, not good.

Fast forward to today. The car was test driven at Lime Rock by a professional race driver who has 1000's of laps at Lime Rock. The setup now for the front is 500 #/in springs, ANZE double bleed shocks, HighStrung44 lower control arms with OEM ball joints, MO30 26.8 mm sway bar, delrin bushings for front sway bar; and the rear is the existing 31 mm hollow torsion bar, 19mm Porsche 3 hole adjustable rear sway bar with delrin bushing in the mounting brackets and spherical bearing drop links.
Corner balanced as before to 50%, front suspension settings are camber -3.5, caster +5.0, toe out total 1/16 in and rear sway bar full stiff with the standard other settings. Tires are 8"Î15 all square R7. Front tire hot pressure was 36 psig and rear tire hot pressure was 35 psig. The car as tested was understeering in right handers, especially turn 1 and was better in the the left hander. The car understeers at corner entry and specifically turn 1 is trail braking to at least the first apex

My pathforword is to determine if there is binding in the front suspension +/- 2 inch around normal ride height, and then in full droop, determine camber change from normal ride height as previously described for binding, and determine bump steer. This data might explain some of the anomalies but there could be other unintended consequences.

What are you and other PCA SP2 and SP3 racers running Ford front and rear suspension components and setups; and why and where, and are they different for different tracks?

I want to have fun, currently like the challenge but it has to resolved 🔜🔄 so it can be a 😃

Last edited by T&T Racing; 06-14-2019 at 08:05 PM.
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Old 06-15-2019, 11:48 AM
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Looks to me you have the right parts on the car. A bit limited in the rear with the torsion bars for adjusting, but all and all the car should be able to be tuned to handle the way you desire.

My first recommendation is to talk to or have Karl Poeltl of Racers Edge help you with the set up. While he drives sp3, the cars are close in handling to the sp3 cars. No one more capable.

Set ups can vary based on driver style. What works for one not always the best for all. Of course with understeer the general idea is to make the front softer to dial some of that out. For me, I would run the same tire pressure all around, and lower overall. Maybe even lower a touch more in the front to improve the oversteer. If that doesn't do it for you, soften the sway bars in frt some.

But, once again, go to the pro for the best advise.
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Old 06-15-2019, 03:30 PM
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Originally Posted by 944Cup View Post
Looks to me you have the right parts on the car. A bit limited in the rear with the torsion bars for adjusting, but all and all the car should be able to be tuned to handle the way you desire.

My first recommendation is to talk to or have Karl Poeltl of Racers Edge help you with the set up. While he drives sp3, the cars are close in handling to the sp3 cars. No one more capable.

Set ups can vary based on driver style. What works for one not always the best for all. Of course with understeer the general idea is to make the front softer to dial some of that out. For me, I would run the same tire pressure all around, and lower overall. Maybe even lower a touch more in the front to improve the oversteer. If that doesn't do it for you, soften the sway bars in frt some.

But, once again, go to the pro for the best advise.
Karl did provide me guidance on a staring point for the front spring rate and sway bar diameter. The sway bar is MO30 and not adjustable. I did increase the tire pressure in the front compared to the rear but overall higher not lower. One area to tune the next time.

The unknowns that are to be dtetemined: is there suspension bind from +2/-2 degrees lower control arm movement at ride height?; what is the camber from +2/-2 degrees of lower control arm movement at ride height?; what is the scrub radius at ride height?. This data should indicate if the kingpin angle is set properly or the strut shaft mounting bearing moved towards the engine or towards the wheel. Also, I can determine what is the best static camber setting.

For now, the path forward is to work the front suspension and not reindex or change the torsion bars. When I bounce the front susoension and then the rear suspension there is very little jounce compared to the rear. So, I believe the front should be a little softer. Make sense?

Last edited by T&T Racing; 06-15-2019 at 07:25 PM.
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