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The Strut thread - Koni / Illumina / Tokico / Carrera / Bilstein / Ground Control

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Don't mean to revive this thread but I figured this is the best place to post this.  So after reading a gazillion suspension posts I'm not 100% on the setup I want to run first. It seems that what works for one person doesn't really work for others so I will take everyones opinions openly. I'm looking to achieve a tolerable street car that will really shine on big road course's in the Socal area.   I'm asking for this groups personal recommendations on which springs I should run. I have the following pairs of springs to try (all are 10"/2.5"); 250lbs, 275lbs, 300lbs, and 350lbs.  Here's my current setup:

 

1971 240z series 2, L28et with JWT 550HP kit.  225/50/16 BFG Rivals. 

Full interior, half cage, TTT front tri brace, rear strut bar, no visible rust anywhere.

 Tokiko Illuminas on sectioned struts 10"/2.5"/300lb front, 10"/2.5"/275lb rear. Z31 CLSD 3.7. 1" front bar, 15/16" rear bar both with semi-adjustable end links.

Stock front brakes with rear disc conversion.

 

Currently getting installed:

Silvia S15 R200 helical lsd with full TTT rear end conversion, TTT front and rear coilovers (with roll center adjusters-front, lowered/corrected rear control arm mounts-rear), camber plates all around, and non-adjustable Bilstien sports. 

 

Willwood 4 piston front, 240sx rear brakes.

 

Currently (old setup) the back end squats a ton when accelerating. It's a little bouncy on the street no matter the setting but considering the right rear is blown and the other dampers are on the same path, it handles really well. Hooks up quite well going straight and around the corners for 450ish rwhp. Around corners it's max grip is as good as my stock evo X on Pilot Super Sports but takes much more effort to do so, obviously. 

 

So which springs do you think I should try first?  My gut says 300f 350r, but after reading everyones posts I'm leaning toward a much softer combo. I just think the rear will still squat too much with anything less than 300 lbs.

Edited by Timecode

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The blown and weak dampners aren't helping the situation diddly Squat ( Pun intended ) . With new shocks and ones that aren't blown, I think you'll find the rear squat is much less. With big HP RWD cars I've always preferred a rear spring combo that is more subtle ( softer ) helps put the power down on corner exit and over bumps.

 

Rain is another concern in the PNW, something that you probably don't have to deal with in sunny California. But weather does have to be taken in consideration for setup.

 

I'm thinking 300F/275R myself..... Whatever you choose, nothing beats Test time on the Track.  

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The blown and weak dampners aren't helping the situation diddly Squat ( Pun intended ) . With new shocks and ones that aren't blown, I think you'll find the rear squat is much less. With big HP RWD cars I've always preferred a rear spring combo that is more subtle ( softer ) helps put the power down on corner exit and over bumps.

 

Rain is another concern in the PNW, something that you probably don't have to deal with in sunny California. But weather does have to be taken in consideration for setup.

 

I'm thinking 300F/275R myself..... Whatever you choose, nothing beats Test time on the Track.  

 

Wouldn't the springs effect squat more so than the damper?  I know the damper makes a difference but it's mainly there to control the springs motion.  The spring rate should decide how much it will compress. Correct?

Edited by Timecode

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I didn't say that dampers affect squat MORE than springs. Both shocks and springs work together. Dampers not only control spring motion, but they also highly affect ALL Transition phases. Shocks control dynamic weight transfer rate and have a great effect on all aspects of handling. Slow Damping is especially critical for transitional phases.

 

Dampers are just one part of the tuning equation, as are springs, suspension geometry etc. . But if you have ANY weak link in the equation ( IE: weak and blown shocks ) then that throws everything out of whack. 

 

Squat is a transition phase just as Nose lift or Roll is. Dead or weak shocks will negatively affect all transition phases, including Squat, Dive and Roll. You can't get any meaningful data with dead shocks. Put the new shocks in first. Test and then decide if you need to change spring rates. 

 

There used to be an excellent article on Sim Racing for setting up Race Car simulators. The damper section was written by a Koni engineer and was taken from a Koni setup guide for real race cars.  I'll see if I can find the link. 

 

Edit: Found it. Well worth saving and printing. Enjoy:

 

http://alison.hine.net/sims/gp2-jw.htm

Edited by Chickenman

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I guess I like stiff things.

Changing out my 550 rear springs for 650 prior to this weekends upcoming race. I think the fronts are 550 or 600. Can't recall. No rear bar, can't find room for any of them. 8611s all around for now but they are taking a beating.

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^^^^^^^^^^^   Er,..

No, went the other way after some revised mathematics and PSI finished the shock dyno.

Trying the Koni's on a lighter setting with a lighter spring and more roll-bar.

 

Racing this weekend, will see how it feels.

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