Lateral Gs

Discussion in 'Suspension and Chassis' started by desmo900, May 13, 2018.

  1. desmo900

    desmo900 TMO Intermediate

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    What kind of lateral G loads are you guys seeing on track? The pic below is from a recent outing I had.
    [​IMG]


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  2. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    Aim Solo

    Accelerometer readings 1.jpg


    Norm
     
  3. desmo900

    desmo900 TMO Intermediate

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    Thanks Norm, what suspension mods are you running?


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  4. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    A little of this, a little of that.

    At the time of those numbers (taken on NJMP's Thunderbolt course):
    Koni yellows, Strano/Hellwig sta-bars (35f/22r), UMI rod-ended endlinks for the front bar, Steeda HD strut mounts (about -1.9° camber), Currie rear LCAs (non-rodend spherical/DIY-modified poly), 285/35 MPSS tires on 18x11 F14 Forgestars, 2008 Mustang GT OE springs.


    Norm
     
  5. desmo900

    desmo900 TMO Intermediate

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    Interesting and eclectic mix of parts there! Most interesting is your use of OEM springs. Did you not want to lower the car for CG benefits or did you determine the stock ride height was preferable?

    I’m running the following:
    Whiteline f/r swaybars (both at full soft)
    Whiteline UCA
    MM LCAs and relo brackets
    Koni yellows
    Vogtland sport springs (est 250/225 f/r lbf/in)
    MM CC plates at -1.4* camber
    Apex EC-7 19x10” wheels
    Michelin PS4S 285/35/19 square @ 34 psi cold
    BMR panhard brace
    MM adj panhard bar

    My transitional response is a bit slow through turns so I’m thinking I may need to stiffen up the front ARB but overall the car feels pretty neutral.

    Patrick


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  6. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    For a dual-purpose car, dropping the CG height is overrated (a 1.5" lowering means about 7% less lateral load transfer, which might buy you 5% more outside tire grip, maybe 4.x% more total lateral grip). Suspension geometries take a hit, and the geometric roll centers do not drop either equally or proportionally which puts you in the position of having to do still more in terms of supporting mods to get the handling balance back.

    You'd chase this for W2W, TT, or serious autocross competition - where you'd probably be trailering the car to those events, not for HPDE or casual autocrossing that you drive the car to.

    Truth be told, I'd seriously considered the Vogtland springs in the beginning, like before I even had my '08 in the driveway. But then I put everything suspension on hold and waited for the car to tell me more. Turns out I don't even like the appearance of wheels clearly not being centered in their openings (makes the car look just as overloaded as the time I brought a load of patio blocks home from the big-box hardware & garden store). Sure, the gap at the top gets tighter . . . but the gaps down at the bottom of the bodywork get bigger. Beats me why so many people can't seem to see the whole picture . . .

    I've always run the front tires on any RWD car about 3 or 4 psi higher than the rears, with any set of tires (I've always run fully 'square' wheel and tire setups). That's been about 35f/31r cold for street driving, and something like 37-38f/34-35r hot at HPDE. Transitional and turn-in response improves while allowing a little extra rear mechanical grip for on-throttle exiting the corners. Mid-corner understeer is reduced a little as well.


    I've since swapped the OE springs out for BMR's GT500 Handling springs (260/220), which necessitated a rear sta-bar change to Strano's 25mm bar. The car is about 0.6" lower in the suspension than before, and I'm considering a very slight lowering of the axle-side LCA pivot. Slight as in about 5/8", for axle roll steer reasons only (I'd really like to work up some kind of fine adjustment capability for this). For that minimal amount of lowering - which I might still shim away a little of - I don't seem to need as much more anti-squat as the aftermarket relo bracket options provide.


    Norm
     
    Last edited: May 15, 2018
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