spring rate advice for street/track car

hey guys i have been trying to figure out spring rates for my street car and my freind jon k reccomended i talk to yall. My plan is too use koni yellows. In the front i was going to move the bottom of the shock housing and adjust the spring pearch hight so dont have to worry about bottoming out the shocks or coilbinding. In the rear iam going to run a eclipse koni yellow, as according to koni it fits perfect and has external dampening change. the valving however is a little more agressive. i had D2 racing coilovers on the car with first 9/7 kg/mm and then 7/5 kg/mm with a stock front bar and thicker rear bar off a hicas car. these are common rates for "JDM" coilovers. the car was balanced on the track and i liked it. but when i called Ground control they reccomened like a 450 lb/in front and a 250 rear. a difference this big seems like it would cause alot of understeer. i noticed some of yall run a simmlar difference in spring rates with no rear bar...to me this seems like it would be really understeery....i was wondering if i could get some clairification on why all these setups work and some reccomendation for my street/track set up. i generally run on street tires but may move up to RA-1s soon. any input or help would be greatly apreciated
thanks
-ben

We can probably be of more help if we know what kind of car you have...

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Originally posted by x-ring@Jan 13 2006, 02:09 PM
We can probably be of more help if we know what kind of car you have...

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dang it....i always forget to put stuff like that in. its a 93 240sx...DOHC

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Originally posted by meatman10523@Jan 13 2006, 07:45 PM
dang it....i always forget to put stuff like that in. its a 93 240sx...DOHC

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we run Koni yellows and those rates with ground controls (450F/250R). We also run the large suspension techniques swaybars front and rear. The car does not understeer at all. It is extremely nuetral. You can get the tail out if you really try, but that usually means you're not smooth anyways. We like it.

Though I would tend to think that spring rate would be a little rough on the street.

s

I agree on the roughness factor.
I used my current racecar ( 90 240SX ) as a daily driver/funday track car with 450 front and 300 rear springs, and koni yellows... it gives your spine a healthy thumping on potholed streets, which is all we have in northeast ohio

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Originally posted by stevel@Jan 13 2006, 04:17 PM
we run Koni yellows and those rates with ground controls (450F/250R). We also run the large suspension techniques swaybars front and rear. The car does not understeer at all. It is extremely nuetral. You can get the tail out if you really try, but that usually means you're not smooth anyways. We like it.

Though I would tend to think that spring rate would be a little rough on the street.

s

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I run a very similar setup, with Koni yellows, 450/325 F/R springs, Whiteline front bar, stock rear bar, and GC camber plates. With around -3 degrees camber on the front and something like -1 degree on the rear I've never had even a hint of understeer; as Steve mentioned if anything the rear tends to step out if you get a little too aggressive.

I can't even imagine trying to drive on the street with this setup; I had a set of much lighter (225/175) springs on the car when it was a street/track car, and even those with the Konis beat the crap out of you.

hmm so from yalls expierence do you think the 325/250 setup will work, for now iam running same size khumo mxs at all 4 corners and i also have some front and rear whiteline bars. do yall run staggered tire setups??? iam just trying to understand how setups that seem so drastically different all work so well

The setups are actually pretty similar, spring rates (to an extent) are pretty much personal preference. The endpoints for springrate are: low end-has to hold up the car, and high end-your shocks have to be able to handle them. I prefer a more "go-cart" like feel, and I now have moved from 450F/300R to 600F/450R although on rough tracks (such as my home track, Nelson Ledges) I go back to 450/300
Your 325/250 setup is a good place to start. As you get more used to the car and get faster on the track you'll probably end up changing things around.(assuming it eventually stops being used on the steet)

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Originally posted by mgp240@Jan 14 2006, 09:54 PM
The setups are actually pretty similar, spring rates (to an extent) are pretty much personal preference. The endpoints for springrate are: low end-has to hold up the car, and high end-your shocks have to be able to handle them. I prefer a more "go-cart" like feel, and I now have moved from 450F/300R to 600F/450R although on rough tracks (such as my home track, Nelson Ledges) I go back to 450/300
Your 325/250 setup is a good place to start. As you get more used to the car and get faster on the track you'll probably end up changing things around.(assuming it eventually stops being used on the steet)

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mgp240 - what shocks are you using with the "go-cart" set up?

I'm still using koni yellow, I talked to Ground Control when I was thinking about switching to heavier springs and they told me the koni's could handle up to about 700 pound springs. I don't know about going up that high, but they still do a good job with my 600's.