Teh Cone Dodgin' STX Wagon - Page 5
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This is a discussion on Teh Cone Dodgin' STX Wagon within the Motorsports Talk forums, part of the Community - Meet other Enthusiasts category; Funny that we are going through almost the same issue at almost the same time. I may have to start ...

  1. #61
    Registered User ButtDyno's Avatar
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    Funny that we are going through almost the same issue at almost the same time. I may have to start a Big Front Bar Anonymous or something. I can't wait to get another 27mm Whiteline on the car.

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  3. #62
    Registered User wrx wagone's Avatar
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    Quote Originally Posted by ButtDyno View Post
    Funny that we are going through almost the same issue at almost the same time. I may have to start a Big Front Bar Anonymous or something. I can't wait to get another 27mm Whiteline on the car.
    Yeah, I have that Perrin set to full stiff and I hope it does the trick as I also sold my 27mm Whiteline during the off season.

    Quote Originally Posted by me during offseason
    What will I need this for? I have stiffer springs now.


    I am skeptical that I will need to go as stiff as the Whiteline. Last year even with 257lb/in JDM pinks, the car had a bit of steady-state understeer in fast sweepers. I think that bar with the springs I have now would be too much. I hope the Perrin does the trick. *crosses fingers*
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  4. #63
    Registered User Pzary3233's Avatar
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    Man I hear ya on putting on the events! I'm doing my first event as Solo chair this next weekend! I'm nervous!

    Sounds like fun but a loose rear isn't always a good thing...

    I guess the higher rates that you have are a bit different, because my 22mm bars front and rear make the car feel about right. I also keep forgetting that you have a wagon.
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  5. #64
    Moderating on the run! Big Sky WRX's Avatar
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    interesting you and John had very similar experiences- bump up spring rates, decrease sway bars (which makes perfect sense btw) and ending up w/ the same conclusion- a bigger front bar is needed

    <--makes note in journal- do NOT sell front bar if I bump up spring rates
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  6. #65
    Registered User ButtDyno's Avatar
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    I have a theory on that one...

    Do sway bars really do anything? - IWSTI.com: Subaru STI Forums
    Quote Originally Posted by stretch View Post
    To get as much roll resistance with springs as you do with a 27mm front sway bar, you'd need to increase your main spring rate up front by nearly 1370lb/in (for about 1770lb/in total). A more modest 24mm sway adds 860lb/in to your wheel rate, still roughly double what front coilover springs typically do (and four times stock). Either way, sways have a huge effect.
    I only bumped the fronts 50 lb/in. Looks like I had 1320 lb/in left

    Not quite 1:1, but 3.5mm of swaybar is wayyy cheaper, easier and better for ride quality. I just did not realize how huge that difference was in terms of feel and balance until I tried it.

  7. #66
    Moderating on the run! Big Sky WRX's Avatar
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    Not sure how accurate the numbers are, but I'm sure that they add significantly to the roll resistance
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  8. #67
    Registered User wrx wagone's Avatar
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    Quote Originally Posted by Big Sky WRX View Post
    Not sure how accurate the numbers are, but I'm sure that they add significantly to the roll resistance
    I'd like to break down and do the math for bar stiffness at some point, it's not that hard, but the force vector acting on the "arm" of the swaybar probably will not stay perpendicular through the range of motion.
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  9. #68
    Moderating on the run! Big Sky WRX's Avatar
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    clearly they add significantly to roll resistance, having a tough time believing they add as much as Stretch quotes though

    I can just about assure you that adding 1300# springs up front provides more roll resistance than a 27mm bar
    "Simplify and add lightness." - Colin Chapman

  10. #69
    Registered User wrx wagone's Avatar
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    Well, you would need these equations:

    Arc Length:

    s=r*theta

    where
    s = distance
    r = distance from center of swaybar to center of the endlink
    theta = angle of motion (solve for this: theta = s/r)

    Angle of Twist:
    theta = (T*L)/(J*G)

    where
    T = torque on the shaft (solve for this)
    L = length of the shaft
    J = polar moment of inertia of shaft (see below)
    G = modulus of rigidity (steel = 11.2 x 10^6 lb/in^2)

    Polar Moment of Shaft:

    J = (Pi*d^4)/32

    where
    d = diameter of shaft

    Torque:
    T = F*r

    where
    T = torque (solved for above)
    F = Force (solve for this)
    r = distance from center of swaybar to center of the endlink


    After you do some substitutions, algebra, etc. you end up with this:

    F/s = (Pi*d^4*G)/(32*r^2*L)

    where:
    F/s = Force per distance, or lb/in - spring rate
    d = diameter of bar
    G = modulus of rigidity (steel = 11.2 x 10^6 lb/in^2)
    r = distance from center of swaybar to center of the endlink
    L = length of bar (center to center of the bar's "arms")

    If I get some numbers I can make a spreadsheet.
    Last edited by wrx wagone; 05-10-2008 at 04:22 AM.
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  11. #70
    Registered User wrx wagone's Avatar
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    I guess I know what I'm going later tonight.
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  12. #71
    Registered User Pzary3233's Avatar
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    My head hurts....

    I'm running to the car to go play with it instead.
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  13. #72
    Moderator   Sasquatch's Avatar
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    Quote Originally Posted by wrx wagone View Post
    I guess I know what I'm going later tonight.
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  14. #73
    Registered User wrx wagone's Avatar
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    Quote Originally Posted by 04.SPT.WRX View Post
    Consult your roomate ...
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  15. #74
    Registered User Oak1ey's Avatar
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    WTF obviously being a fairly new Scooby owenr I have a lot to learn

    Thanks for the mathematics I understand that completely
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  16. #75
    Registered User wrx wagone's Avatar
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    Quote Originally Posted by Oak1ey View Post
    Thanks for the mathematics I understand that completely
    No problem. A degree in Engineering helps.

    I'll have an excel spreadsheet posted later tonight or tomorrow that should be fun.
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