Let's discuss Subaru sway bar tuning

Discussion in 'Modifications & DIY how-to' started by Porter, Aug 23, 2004.

  1. Porter

    Porter Member

    I wrote this up on another site in a discussion on swaybar tuning and bar sizing vs. over/understeer. There is a common misconception that Subarus understeer because the rear sway bar is too small. This is not the case in practice, and while you can convert a Subaru to a more oversteer-prone bias by stiffening the rear bar, it is not for the reasons that are commonly accepted in a Miata or another "classic handling" chassis type.
    What are your thoughts?


    -Jason Porter
     
  2. miloman

    miloman Retired Admin

    thanks jason... that was a whole lot of info for a noob like me :)

    i took part in the autocross at turner field on 8/22... with my tein flex stiffened up (rear all the way stiff and front 4 clicks softer - as advised by joel fehrman) and running on victoracers, i did pretty decent... in terms of suspension everything else besides the tein flex is stock... the tires did a good job of keeping the car stuck to the ground

    however, i noticed that on some turns, if i was going fast or turning tight, the car would bounce... do u think swaybars would help me here?
     
  3. Alex

    Alex Community Founder Staff Member

    When I get the chance, I will definately add my thoughts to this. At the moment, caught up in something else. Great idea! :bigthumb:
     
  4. Porter

    Porter Member

    If you're getting "bounce" when traveling over road imperfections, either the rebound damping rate isn't turned up high enough, or the natural compression damping rate of the strut is too high.

    Swaybars may help, certainly, but they'll help by changing the way that weight transfer occurs. If the Teins are less "loaded" as a result of body roll, they'll be more able to respond to changes in the road surface.


    Also, how low do you have it? It's possible that you're actually jouncing the suspension down to the bumpstops on full compression, and the bounce you're experiencing is a result of all the rubber pieces in the suspension working together to create a "spring" effect.
     
  5. miloman

    miloman Retired Admin

    i got it set by the guys at knowledge... they set it at the height that joel fehrman had on his wrx... i think its between 1.5 and 2 inches below stock (not too low)... i had turned the dampers to super stiff... and i have 8kg springs... due to these factors, i doubt i was bottoming out....

    this course was anything but flat... sections of the course went over brick walkways and made everyones cars lose some control... i might have benefitted from softening the suspension a little bit
     
  6. Porter

    Porter Member

    Ya, sounds like the compression damping was a little too high.

    If I remember right, the Teins adjust both compression and rebound with a single adjustment, rather than adjusting rebound independently.
     
  7. miloman

    miloman Retired Admin

    i think ur right... there's only one damper adjustment knob
     
  8. WRboXer

    WRboXer Active Member

    so your saying overall a front sway bar will be more beneficial and handle better...while a rear is actaully bad? so should one just skip the the rear sway and just go for the front? what about adjustable rear sway bars, would it help if it was on its softest setting.

    im very interested because i was planning on either a front or rear strut bar, but i only have money for one.
     
  9. Porter

    Porter Member

    In general a front sway bar is more beneficial than a rear bar on a Subaru, but the rear bar needs to be sized to complement the front bar, or you get wacky handling. In general the front bar is the more important of the two, but the rear bar is important too. You can't really address one without addressing the other.

    If you have an 04+ WRX (17mm rear bar) the first upgrade should probably be a rear bar. If you're in a car with balanced sway bars (02/03 WRX 20mm f/r, 04+ STi 19mm f/r) then the first mod should be a front bar.
     
  10. WRboXer

    WRboXer Active Member

    ok, i have an 03. im not gonna have enough money for a front and rear sways. im going to have h&r springs with agx's installed soon, i am planning on a 22mm perrin front sway bar...and later on a cusco 22mm rear sway bar. how does that sound (moderate auto-x use).
     
  11. GTscoob

    GTscoob Black is Beautiful

    interesting stuff. Someday I want to get some coilovers and just spend a long time just playing around with the settings just for the hell of it.
     
  12. Alex

    Alex Community Founder Staff Member

    I was thinking in my grand scheme of things because I dont feel like shelling out for the JDM STi coil overs we just got one, pinks, hsm, front bar should suffice me for a fair portion of my newbie autox life.
     
  13. Porter

    Porter Member

    Sounds like a good plan.

    There's also the new USDM SPT/STi coilovers from Subaru... they're pretty dope. I'm not normally a fan of SPT's stuff but these are excellent struts, it's the same thing you'd walk in and buy from one of the STi brand stores in Japan.

    [​IMG]
     
  14. Alex

    Alex Community Founder Staff Member

    Yeah, we just got the JDM STi coilvers in, they're schweet.
     
  15. longfury

    longfury Active Member

    Another thing to consider is that the Impreza is very nose heavy. Having a bigger front bar helps to raise the front spring rate without stiffining the front springs further and degrading the ride. I have the Whiteline 20-24 rear bar with Whiteline rear endlinks. You can easily see that the front of the car just wallows around. The combonation of the relatively soft front springs and the 20mm front bar shows that the car is nose heavy and the springs and bar are way not stiff enough. I have a 24mm bar that Porter recommended. I finally have the right tools to install it and will be doing that this weekend.

    But Porter is right on with what he is saying. Even with a 22mm rear and the stock 20mm front i still have understeer. I would love to ride with these people that claim they have oversteer.

    -Richard
     
  16. Dacula Dean

    Dacula Dean Member

    This is an old thread that I would like to resurrect because it's striking a chord for me. I just put 22mm adjustable bars on front and rear. Right now, they're both at the 22mm setting. My setup is not where I want it, because I've had a couple of glitches with parts, but I'm noticing that the car is absolutely dreamy when accelerating.

    This is not new, however. The new parts (sway bars and springs, I must admit) have accentuated something that was true while driving stock parts. Once the car gets into its power, cornering is like carving a sweet mogul on skis.

    The key is getting into the power. Due to the turbo lag, I'm realizing that I need to get on the gas before I want to accelerate through the turn. Suddenly, I envy the left-foot brakers. You need to get into the gas to get the turbo spinning, but that has to happen before you want acceleration in the turn.

    So, I'm playing with two thoughts in my head. First, I'm starting to tell myself to get off of the brakes and into the gas before I think I should. Second, I'm wondering how to rig the car to have slight suspension-induced oversteer on braking and coasting, with slight power and chassis oversteer in the last two-thirds of the corner.

    Hat's off to Jason for the post. Cool stuff to keep us thinking.

    Dean
     
    Last edited: Jul 7, 2006
  17. bluetwo

    bluetwo Active Member

    No doubt man. This is a great thread for the most part.

    I can tell you that I have a 27/29 mm front sway and a 22/24/26 mm on the rear. The rear set at 24 and the front at 27, and not only is the car really firm in the corners but it's a really safe feeling car since it like to understeer (A LOT) at the limit of power on corning. I can get the car as loose as I want in the dirt, but it just won't let go in the dry and it even does really well in the extremely wet conditions. I'm riding on Fusion ZRi's btw, and I apoligize if my coments are irrelevent to the rest of the thread.... Just thought I'd share.
     
  18. Dacula Dean

    Dacula Dean Member

    Wow. You've dialed into territory that I haven't considered. These cars can really go where you want them, eh?

    I can't believe that I got an immediate reply to my addition to this thread. Too cool.

    Dean
     
  19. calmnothing

    calmnothing Shlimp Flied Lice Supporting Member

    I'm running 24/24 and it goes where I want. I can plow through a turn and depending on when I apply power and how fast i turn I can get it to slide either way.
     
  20. clemsonscooby

    clemsonscooby Active Member

    I have 20/26 right now. I am looking to upgrade the front. As far as peformance goes, if you don't have camber bolts and a custom alignment all the way around the car will never be nuetral. I dialed out a lot of negative camber in the rear and maxed out the fronts. This really help to get rid of the understeer during hard cornering. Right now, I just have to flick the wheel to get the rear to step out smoothly (no power required). A lot better than when I first started and the front wheels would just plow.
     
  21. calmnothing

    calmnothing Shlimp Flied Lice Supporting Member

    If you wanted to be real daring....

    You could go for a staggered tire setup and use weights to offset it so your center diff won't fry.
     
  22. javid

    javid Member

    Your car should be able to get as loose as you want it on corner entry, just keep practicing the trail braking. Mid corner (neutral throttle) is going to be tough to get loose with out making the car too loose on exit. What is your current alignment?
     
  23. Dacula Dean

    Dacula Dean Member

    Okaaayyyy.....

    From mid-corner on I'm happy.

    Front:
    Camber -1.7degL / -1.8degR
    Caster 2.8degL / 3.0degR (stock)
    Toe 0.05inL / 0.06inR

    Rear:
    Camber -1.5degL / -1.3degR
    Toe 0.05inL / 0.03inR

    Hmmm. Now I'm wondering about the units on those toe numbers. The sheet I have says '0.05".' That '"' could be either inches or seconds. Lookiing at the service manual, 0.05 would be within the spec's using either unit.
     
    Last edited: Jul 13, 2006
  24. clemsonscooby

    clemsonscooby Active Member

    You should try to go less with the negative camber in the rear next time. It makes a big difference when you come into a corner hot.
     
  25. mpaone

    mpaone Member

    I have nothing to add other than the fault of the rear bar only upgrade is more evident on fast sweepers and decreasing radius turns. It only took me one spin at the Dragon to be cautious about just upgrading the rear bar next time.

    -Mike.
     
  26. javid

    javid Member

    Right less rear camber if you can only get 1.8 out of the front.

    I have 2.5 front (with the ball joint extenders, so like -3.3 for you lowered guys) and run -1.5 in the rear.

    Your toe read out is in degrees and those numbers are the same a zero. 1/2 inch toe on a standard toe plate is about 1 deg.
     
  27. mmtasty

    mmtasty Active Member

    "...exacerbates..."

    oooh Mr. Fancy Pants... $.25 to you.

    Good info! I'll be sure to go larger up front. I'm working up the money for coilovers, front and rear sways, and an ALK all at once.
    Maybe someone could give some info on another useful suspension part I should do while I'm at it so I only have to pay for one alignment.
     
  28. socrates42

    socrates42 Member

    ^^endlinks and groupN tops.

    My camber settings made all the difference in the world. Car became much more flickable with understeer to start, then with a little trail brakeing, oversteer/4wheel drift. My current suspension setup is stock with a 19mm stock sti rear bar with whiteline endlinks and camber bolts in the rear.

    My alignment settings are as follows

    1.5degF, 0 cross camber
    .006 toe front, 0 cross toe

    1.2degR, 0 cross camber
    .005 toe rear, 0 cross toe

    I think next time I might go with 1.5 front, and 1.0 rear
     

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