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Right springs for Autocross/HDPE Events

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898
544
There are several forum members that run a 600 front / 350 rear spring rate on our Boss track cars combined with a 35mm front bar and 18mm or smaller rear bar. This setup is used with tires ranging from 295 F / 315 R to a 315 square setup with good results. With driver, the car weights are around what you discussed above.

If this was a dual purpose street car, I would recommend a rear spring rate of 250 - 275 lb/in and running a larger rear bar. The larger bar helps maintain roll stiffness and the softer springs provide better ride quality. The downside to this is a little bit less rear corner exit traction on track because the larger bar will lift the inside tire more than a smaller bar.

I personally run 550 F / 350 R springs with a 35mm Strano front sway bar set to full stiff, a 18mm Ford rear bar, and 315 R7 square tires. The combination works pretty well. If I were to do anything, I would change to a 600 lb front spring and set the front sway bar to the middle setting.

My setup has some mid corner push, but not anything like the OEM Boss suspension. The upside to the combination is exceptional rear grip on corner exit that really allows early and hard throttle application.
 
898
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I forgot to add that I would email Cortex your weights, tire selection, and other suspension setup information. They will be more than helpful in providing a detailed recommendation, especially to an existing customer.
 

Grant 302

basic and well known psychic
Welcome to TMO zajac. For track only use, I think you're looking at the right rates at 600F/350R. I'd ask Filip if your Konis are valved to handle higher rates like that, considering that they don't have separate compression/rebound adjustments. My understanding is that higher spring rates might need to 'blow off' more/sooner on the high speed compression.

I'm running the CorteX/JRi DA units with 550F/350R with 305 slicks and I feel like I could use more spring up front in my '11 GT on the track. IIRC, the FR500S used 500F/300R and the later 302Ss used 800F/400R and I think a little less for the earlier ones.

Not sure I'm helping here, but I think you're going in the right direction to run slicks. I absolutely agree with your stated 'philosophy'.

Maybe @Mad Hatter has more to add since he's running the Koni units.
 
100
109
Utah
I have good news and bad news.

The good news....

I figured I may as well close the loop and report back on my questions regarding upgrading the springs on my 2007 Saleen PJ Mustang. As suggested, I contacted Filip at Cortex to confirm what springs I have been considering for upgrading my Saleen PJ with current 475 lb and 275 lb springs. The key part of the question was whether upgrading to 600 lb and 350 lb springs would be compatible with my current Cortex Koni yellow coilovers with the "track valving" option. The answer from Filip was the the koni yellow coilovers w/track valving would have no problems with 600 lb and 350 lb springs. So that is the good news. The Forgeline 18x11 wheels are on order as well as the 315/30/18 BFG R1S tires. Next will be the 600/350 .250 x 8.00 springs.

The bad news...

Here in Utah the Miller/UMC track season is over and will not start up again until March of 2017. The four month downtime allows for much thinking, wishful spending and plenty of time for installation mods.

Another unrelated item, the Auto-Blip mod seems pretty cool since I am very mediocre at rev matching on down shfts. My C7 Corvette with rev match makes me not only sound good but also makes me look good as If I know what I am doing on the track. So Auto Blip will be great, especially since I think my Saleen PJ Mustang with Kooks LT headers, no CATs, Ford Racing mufflers, sounds a whole lot better than my C7 Corvette (2 CATs removed, Borla X pipe).

zajac
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
zajac said:
I have good news and bad news.

The good news....

I figured I may as well close the loop and report back on my questions regarding upgrading the springs on my 2007 Saleen PJ Mustang. As suggested, I contacted Filip at Cortex to confirm what springs I have been considering for upgrading my Saleen PJ with current 475 lb and 275 lb springs. The key part of the question was whether upgrading to 600 lb and 350 lb springs would be compatible with my current Cortex Koni yellow coilovers with the "track valving" option. The answer from Filip was the the koni yellow coilovers w/track valving would have no problems with 600 lb and 350 lb springs. So that is the good news. The Forgeline 18x11 wheels are on order as well as the 315/30/18 BFG R1S tires. Next will be the 600/350 .250 x 8.00 springs.

The bad news...

Here in Utah the Miller/UMC track season is over and will not start up again until March of 2017. The four month downtime allows for much thinking, wishful spending and plenty of time for installation mods.

Another unrelated item, the Auto-Blip mod seems pretty cool since I am very mediocre at rev matching on down shfts. My C7 Corvette with rev match makes me not only sound good but also makes me look good as If I know what I am doing on the track. So Auto Blip will be great, especially since I think my Saleen PJ Mustang with Kooks LT headers, no CATs, Ford Racing mufflers, sounds a whole lot better than my C7 Corvette (2 CATs removed, Borla X pipe).

zajac
I love my koni cortex setup. I have 600/350 springs with rear shocks full soft I found the street ride better then P springs with oem boss shocks on full hard. Have a 24mm rear bar and switching to a 18mm thanks to Grant. Front adj BMR bar is in the middle setting (hate understeer). I was thinking about going to 800 front springs but as it is, curbing the car gets a little unsettling.

On the way to one of our tracks, we have a lousy highway section about 30km long. With the stock shocks and oem or P springs the car would start to occilate up and down. With the cortex koni setup the car feels far better and you hardly notice the bumps.



Sent from my SM-G900M using Tapatalk
 

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