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  • set-up advice

    I just came back from my first track day without a rear sway and I must say that it is a massive improvement. Unfortuanetly though there are some undesirable side effects. First of all it lifts the inside front tire when I am accelerating off a tight corner, which really isn't much of a concern since the car is absolutely perfect handling feel wise under those conditions. The main problem is that it seems to have a bit too much corner entry understeer, which goes away completely when I get on the throttle. On the throttle the car is 100% stable and planted, but still rotates nicely. Off the throttle it understeers more than I would like. Right now I am running 9k fr and 7k r springs with a cusco 28mm hollow front sway bar. To start I know I need to get an adjustable front sway bar, I was thinking the progress 27mm hollow bar as it comes with nicely done spherical endlinks and the adjustments cover a pretty wide range from what I have been told. Playing with the sway bar will help, but I am not convinced that it will 100% solve the problem. I am also considering putting the stock 15mm rear sway on, but I really don't wanna give up the on-throttle feel of the car and that would change that. I could also tinker with the shocks if they were double adjustable to try to slow down or speed up the weight transfer, but unfortuanetly they are not double adjustable. I was also thinking that a little less static camber combined with a little more caster may also help with my problem. I just wanna know if anyone has any other ideas and verify that I am on the right track here.
    function > form
    1990 240sx fastback: IN PROGRESS

  • #2
    What are your alignment settings. I've sometimes found a "lazy" car off throttle have a little too much toe in on the rear. What's your front/rear camber? I'm assuming you're running about zero toe, or just a hair of toe in up front for braking purposes.

    Lifting the inside front isn't necessarily a bad thing, but it might mean that your front is just TOO stiff in comparison, thus making the rear almost "fall over" on itself in a transition into a corner in comparison to the front.


    What dampers do you have? Even though I don't have a full 861x setup on my car yet, just changing out the fronts to 8611s and having useful compression/rebound response made a world of difference towards making the front feel like it was usefully transferring weight vs. feeling like a "stiff board... that's dead" with the K-Sports(bleh).
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


    DefSport Koni Sleeve and Spring Perch Buy!!!
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    • #3
      My front specs are:
      caster- 7*
      camber- 2.8*
      toe- 0

      Rear:
      Trac arms shortened 3/8" from stock length
      camber- 2.2
      toe- 1/16" in

      For my next alignment I was planning to change it a bit though.
      Front:
      caster- 7.5*
      camber- 2.5
      toe- 0

      Rear:
      camber- 1.5 to 1.8 (undecided)
      toe- 1/16"in (maybe try 0 since the rear is planted so good now)

      I am running tein flex coilovers. I have them adjusted a few clicks below full stiff in the front and one or two clicks above the middle in the rear. I really don't think playing with the knobs on my shocks will do anything but make me feel better though.
      function > form
      1990 240sx fastback: IN PROGRESS

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      • #4
        Lifting the front isn't that bad, as far as I've seen, most fast cars with struts up front (i.e. BMWs) are running enough front roll stiffness to just lift front wheels on really tight corners (autox). If it feels fine, even with the wheel in the air, then what's the problem?

        To help the understeer, you could try 1/16th toe out up front or bump the rear spring rates up 50lbs or so.

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        • #5
          Here's my setup:

          Front:
          600# springs
          8611's - 1.5 turns rebound, 3 clicks compression (from soft)
          3.1 deg camber
          1/16th toe out

          Rear:
          450# springs
          Koni Yellows - Rebound full stiff
          1.5 deg camber
          1/16th toe in

          I'll try to measure up my traction rods later.

          With tire pressures dialed in, the car is still loose on corner entry. With my rear pressure too low, I was spinning out while braking into corners. These are pretty old tires though (V710s maybe a couple years old). I'll have a better idea of what the car is doing in 2 weeks when it's on fresh Hoosier A6's.

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          • #6
            I can see what you are doing with your shocks and wish I had the 8611's so I can do the same. I think it may be a weight transfer problem as the car is perfect once I get on the throttle and transfer the weight back. That tells me that the outside front tire is over loaded. If I could stiffen the front compression and soften the rebound it would slow the weight transfer to the front and allow it to come up faster. Then I could soften the rear compression and stiffen the rebound which would allow the weight to transfer back easier and the stiffer rebound would slow the transfer back to the front. Since I can't do that, yet, I think I will drop the rear down about 1/4", set the rear toe to about 0 (just a nuthair in), and set the front toe just a nuthair out (maybe 1/16, maybe less I haven't decided yet). I am thinking I will decrease my rear camber to 2.0 and increase the front to an even 3.0. Before the next event I am hoping that I can get the progress front bar, but I think they are pretty backordered. That will give me some more room to adjust.
            function > form
            1990 240sx fastback: IN PROGRESS

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            • #7
              BTW - what's your reasoning for setting the traction rod 3/8" shorter than stock? Have you measured the bumpsteer with your alignment settings and compared it to the stock traction arm length?
              '18 Chevrolet Volt - Electric fun hatch for DD duty!


              DefSport Koni Sleeve and Spring Perch Buy!!!
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              • #8
                Actually shortening the trac arms up a bit was a suggestion that ace gave me on zilvia a while ago. I'm not 100% surte on the theory behind it though, you should ask him about that. It seems to make a difference as even before I removed the rear sway, and after I shortened the trac arms, the rear was biting quite a bit better.
                function > form
                1990 240sx fastback: IN PROGRESS

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                • #9
                  We should scrape some $$$ together as a group to buy a bumpsteer gauge and measure S13/S14 suspension with stock length arms then go through some different lengths and plot up bump steer graphs.

                  As far as your car biting, I'm kinda with Carroll Smith in that front toe shouldn't really be anything other than right around zero for a door slammer. I think your car not wanting to "turn in well" is related to the dampers more than anything. I noticed a huge difference just going to front 8611s and getting some more reasonable low speed compression/rebound - the turn in change was astounding. The rates were about the same(7 kg/mm if you can believe the cheap K-Sport springs vs. 7.5 kg/mm Eibachs), and nothing else changed. The dampers had a huge difference in how the car behaves in a transition - beyond even what I was expecting, and I was expecting a lot.
                  '18 Chevrolet Volt - Electric fun hatch for DD duty!


                  DefSport Koni Sleeve and Spring Perch Buy!!!
                  http://www.nissanroadracing.com/showthread.php?t=5902

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                  • #10
                    Originally posted by Def View Post
                    I noticed a huge difference just going to front 8611s and getting some more reasonable low speed compression/rebound - the turn in change was astounding. The rates were about the same(7 kg/mm if you can believe the cheap K-Sport springs vs. 7.5 kg/mm Eibachs), and nothing else changed. The dampers had a huge difference in how the car behaves in a transition - beyond even what I was expecting, and I was expecting a lot.
                    I noticed this as well. The turn-in with the Konis + Progress bar up front is awesome compared to my old setup. Other people who have driven my car have said the same thing.

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                    • #11
                      That's the low speed damping at work. Toe-out up front does help a bit, though.

                      When I did my rears, I basically used a floor jack and eyeballed it. Shortening the rear trailing arms had a decent affect on the spindle's rotation about the lower ball joint, and it also gave me a bit more camber gain. I'll have to check the toe affect, perhaps by measuring with toe plates with the rear end jacked up and squatting (removed rear shocks).

                      I have access to a bumpsteer gauge but the guy hasn't responded to me about doing an alignment. I'll see about getting onto his alignment rack later, but waaay too much stuff going on. It probably won't happen untill after the Tour event in 2 weeks, when I install the 8611's in back.

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                      • #12
                        The shorter trac arms definitely increase camber gain and that is the primary reason that I want to decrease my rear static camber.
                        function > form
                        1990 240sx fastback: IN PROGRESS

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                        • #13
                          I'm going to go ahead and agree with everyone else. The way your car feels steady state tells you that your roll stiffness distribution is where it needs to be, but since its pushing on entry then you have a transient problem. Playing with the dampers would definitely help your situation, but since you can't do that on your current setup I think you're on the right track with adding toe up front.
                          92 Coupe

                          www.terpsracing.umd.edu

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                          • #14
                            I would just be cautious with making 10 changes at a time like you talked about.
                            -Ryan

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