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  • Light Car Spring Rates?

    Alright guys, I'm going to be biting the bullet and buying an 8611/GC combo from our host, so I need to figure out my spring rates.

    My car is currently hovering around 2270lbs. It will be no heavier than 2350lbs after I'm done. I don't have an issue of sticking with class rules because I hate all the classes, so no worrying about that.

    Should I go with something simple like a 500/400 or stick with 450/350 or even 475/375?

    Setup will probably end up being 285/30R18s all around, R888s likely.

    No autocross, only track days and street driving.

    Any ideas or experience?
    S13
    1:31.xxx CW/CCW SoW
    1:04.837 CW HTM
    ?? Chuckwalla
    ?? BW13

  • #2
    Any of those rates will be fine, but IMO on slightly bumpy tracks you'll gain just as much from a little compliance in the suspension from softer rates as you are giving up to the stiffer setup in smooth sections. On seriously bumpy tracks you are talking about the softer setup being much easier and faster to drive.

    There isn't a huge difference between the rates you posted, but I'd say something in the 450-475 range up front is a good start.

    It's also much easier to drive on the street with softer rates that are more compliant, not just from a comfort standpoint.
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    • #3
      What's the front/rear balance? What sway bars? What wheels? What roll center heights? What CG height? What else?

      That's what you need to know if you want to pick spring rates.
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      • #4
        Front/rear balance is about 54.5/45.5. Sways are Whiteline front and rear, going to be switching to either a Largus or custom hollow sway setup of similar stiffness in the front.

        Wheels will be 18x10.5 RPF1s.

        Roll center heights are unknown, as is the cG height. cG is lower than most S-chassis, though.

        The tracks I frequent are the Streets of Willow Springs and Horsethief Mile at Willow Springs. I will be making road trips to Laguna Seca, Buttonwillow, Infineon, Phoenix International, etc.

        I drive my car to the track, however I also drive my car on the street for pleasure, so I want something that's somewhat of a compromise but erring on the side of track-oriented. I currently have 450/340 and they're awful, but proper damping eludes KTS' engineers and they were better when they didn't have 45k on them.
        Last edited by SOneThreeCoupe; 05-27-2008, 10:37 PM.
        S13
        1:31.xxx CW/CCW SoW
        1:04.837 CW HTM
        ?? Chuckwalla
        ?? BW13

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        • #5
          I like my 9k/7k set-up for the most part and out cars are pretty similar. The only bitch is that without the rear sway the car has understeer off the throttle, but that is just as likely my shocks or alignment as my springs. It is highly doubtful that you will get it perfect on the first shot anyways so I would just get in the ballbark to begin with and you can always change the springs later if you feel it necessary. I would keep the rears at least 75lb/in softer than the fronts and no more than 150lb/in softer. If you plan on keeping the rear sway in then you should probably be more towards the 150lb/in softer range.

          EDIT: I have been daily driving my car lately as well and it is liveable.
          function > form
          1990 240sx fastback: IN PROGRESS

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