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  • setup help...lifting wheel

    I went to a local autoX today and I was told I was lifting my rear tires during corner entry. What is the proper way of dealing with lifting my rear wheels. I get a little more oversteer than I'd like and my corner exit is not where I think it should be.

    Attempts at helping the issue-
    lower rear tire pressure
    less rear rebound- 1/2 turn from soft (Koni)
    slower entry speeds and different turn in

    other options-
    increase rear droop-How is this done?
    remove rear sway bar (hicas)
    change out 210K+ VLSD-Thinking about putting some heavier gear oil in it. Currently running OEM viscosity Mobil 1 gear oil.
    more rear rebound-I thought this would not help with oversteer/corner exit.
    larger front sway bar-Doesn't seem like it'd help the rear wheels from lifting
    stiffer rear spring rates
    stiffer front spring rates

    44 front psi 37 rear psi (after 3-60sec runs)
    450#front 350#rear springs
    front struts full stiff/rear struts 1/2 turn from soft (Koni)

    My full setup is in my STS blog.
    Addicted to Motorsports

  • #2
    Looking at your blog I would say you have too much camber both front and rear for street tires. (something more like 3 degree's F/ 1.5-2 degree's R and 1/8" toe in rear)

    Remove the rear bar to try and keep it a little more composed as well.
    Between rides...unless you count a WD21...

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    • #3
      Should I run higher spring rates to compensate if I remove the rear sway bar? I'll probably take it off and see how it feels first. You think more rebound would help?
      Last edited by ckcadavona; 03-10-2008, 06:05 AM.
      Addicted to Motorsports

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      • #4
        Less rebound in back, more in front. Remove the rear bar. If you need to, bump the rear springrate up a bit to balance it all out.

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        • #5
          You could also try adding helper/tender springs in the rear.

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          • #6
            Thanks guys...I'll pull the rear sway bar off and see how it works at this weekends autoX. The course is tighter and slower then last weekends course but we'll see.
            Addicted to Motorsports

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            • #7
              I took the bar off and I took a few measurements. From the fender to the center of the hub L16 R16 7/8. From top perch to bottom of strut was 22 3/4 on both sides. I wonder what caused the difference. I measured three times. The car has more body roll now but I'll see how it works this weekend. I might have to start swapping spring rates for every event.
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              • #8
                Your alignment might have changed when the sway bar isn't there putting pressure on pushing on both sides of the suspension, plus the bushings in the arms/spindles are probably more relaxed now, so you'll get a little bit more variations between the 2 sides.
                http://sosideways.wordpress.com/

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                • #9
                  Is your rear spring loose when the car is in the air? If it is, make it not loose. That will help to keep load on the wheel until you get to the point of fully unloading the corner. You need to figure out why the wheel is lifting. I don't think removing the rear sway bar is the answer, especially when it's a HICAS bar, they're stiffer than stock but not that stiff at all. The only reason this would help would be if your springs weren't captive and the load on the outside wheel was lifting the inside wheel due to the sway bar load transfer.

                  What arms are you running in the back? And is this only happening during braking and cornering or under pure cornering as well?
                  www.tipengr.com

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                  • #10
                    I assumed it was the sway bar load transfer that was causing the wheel to lift. That is why I removed the rear sway bar. The car feels much better without it with the exception of the rears spring rates feeling a bit too soft. I have no proof or hard evidence of this being the case with the exception of jacking the car up an noticing the wheel that's off the ground not having any droop or the simple fact that the car feels better without the rear hicas sway bar.

                    I'm running stock arms w/ urethane bushings. From what the corner workers told me it's only happening durnig braking and cornering.

                    Thanks for the feedback everyone. I managed to get the car to where I want and feel it needs to be over last weekends autoX. The spring rates need to be higher but it'll be okay for now while I learn to drive with consistency and for daily driving.
                    Addicted to Motorsports

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                    • #11
                      Originally posted by Wiisass View Post
                      I don't think removing the rear sway bar is the answer, especially when it's a HICAS bar, they're stiffer than stock but not that stiff at all. The only reason this would help would be if your springs weren't captive and the load on the outside wheel was lifting the inside wheel due to the sway bar load transfer.
                      That's pretty much what's been happening to me, even with a stock rear sway (Whiteline bar up front). Tender springs would help, but only as much as the rear sway will allow them to (which reminds me, I need to order some tender springs before the season starts). The same thing happens on BMW's, which is why a bunch of those guys run without a rear sway (or a massive front bar).

                      What arms are you running in the back? And is this only happening during braking and cornering or under pure cornering as well?
                      I was lifting a rear with my car NA at the top of 2nd gear (fast for autox) through some sweepers. I just couldn't plant power with the HLSD, whereas now it's not nearly as much of a problem (even with boost).

                      Oddly enough, DJ McArdle up in NY would lift a front tire on his S13 with the rear bar removed... although I forgot his springrates (I think he posted them on NICO once). For reference, my setup has 600# fronts and 450# rears.
                      Last edited by AceInHole; 03-18-2008, 04:52 AM.

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                      • #12
                        What up ace! Nice to run into you here! You know that the whiteline front bar isn't really that stiff either? The largus bar is hollow shich gives it hoop strength, basically it just has waaaaayyyyyyy more surface area than a solid bar which translates to more surface tension which = stiffer. I plan on running the largus front bar with the whiteline rear bar. But I am working on re-locating the LCA mounting points on my spare subframe to pretty much eliminate the anti-squat. I think that that is the primary problem with the rear suspension on 240's (especially s-13's) WAAAAAAYYYYYYY too much anti-squat. As to the OP's question, try disconnecting the rear sway for sure and maybe stiffen up the front roll stiffness a bit. It is possible that the front is rolling too far and lifting the inside rear tire as a result. Your spring rates sound in the ballpark to me, but ace's rates are much higher and I can vouch that he knows what he is talking about.
                        Last edited by racepar1; 03-23-2008, 11:07 PM.
                        function > form
                        1990 240sx fastback: IN PROGRESS

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                        • #13
                          Originally posted by racepar1 View Post
                          What up ace! Nice to run into you here! You know that the whiteline front bar isn't really that stiff either? The largus bar is hollow shich gives it hoop strength, basically it just has waaaaayyyyyyy more surface area than a solid bar which translates to more surface tension which = stiffer. I plan on running the largus front bar with the whiteline rear bar. But I am working on re-locating the LCA mounting points on my spare subframe to pretty much eliminate the anti-squat. I think that that is the primary problem with the rear suspension on 240's (especially s-13's) WAAAAAAYYYYYYY too much anti-squat. As to the OP's question, try disconnecting the rear sway for sure and maybe stiffen up the front roll stiffness a bit. It is possible that the front is rolling too far and lifting the inside rear tire as a result. Your spring rates sound in the ballpark to me, but ace's rates are much higher and I can vouch that he knows what he is talking about.
                          Hoop strength? I didn't know sway bars were pressure vessels. A solid bar is always stiffer than a hollow bar of the same material and outer diameter.

                          Depending on the wall thickness on the Largus bar, it's probably too stiff, I don't know why people running already high spring rates feel the need to run a stiff sway bar. with the stiffer spring rates that people are running the sway bar has more negative effects that positive. It will decrease your roll gradient, but I mean we're talking less than 1.5deg/g with just springs alone.

                          I don't know, I still don't think this wheel lifting problem is totally rear sway bar related. I think there are other problems that people are overlooking and removing the rear sway makes it a little better, but there's still a deeper problem that is not being addressed. Binding in the suspension, too much rebound damping coupled with no preload or a non-captive spring, etc, something else seems to be happening. Especially with stock sway bars, I've measured them and I'm sure you guys have looked at them, those things couldn't lift the unsprung weight without the loaded wheel being compressed a lot.

                          And if you do remove the rear sway, increasing front roll stiffness is just going to make the car understeer more.

                          And this should probably be another thread, but what points are you relocating and why? I know you think you're going to be getting rid of the anti-squat that you have heard is designed into the rear suspension. But if you're just moving the points that you think should be moved, you're probably going to mess something up. I'm not trying to be an asshole, I just don't want you to waste a spare subframe just because you think you know what needs to be changed.
                          www.tipengr.com

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                          • #14
                            My next step is to run some tender springs in back. I'm planning on starting with a 50lb tender, although there seems to be a gap between 150 and 50 lbs according to the lists on some sites.

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                            • #15
                              I got that information from a guy that has been building racecars for about 40 years and before that he worked inthe aerospace industry, so it is pretty reliable info. I'll send you a PM discussing this though. I will also send you a PM about the mounting points as well. You are right though, for sure there is something else going on. I don't think it is shock related though as shocks are pretty much the smallest adjustments that you can make to the suspension. That's not to say that mis-adjusted shocks won't cause some problems, but I really don't think that they can cause a wheel to lift. To the O.P.: do you have adjustable arms and bearings in the uprights or is it just urethane bushings? If it is just bushings it could be binding the suspension some as the urethane bushings do not articulate very well since they are so stiff. Tender springs might help, but they will not hold as much pressure on the wheel as the rates are MUCH softer so you might still have problems hooking up off the corner. If you can find a way to get the car to squat more it will help keep that wheel down as well, but may start lifting the inside front.
                              function > form
                              1990 240sx fastback: IN PROGRESS

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