What does this picture say??

Discussion in 'Suspension and Chassis' started by Mad Hatter, May 30, 2018.

  1. Grant 302

    Grant 302 OPM Spent: $587,402 Moderator

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    I know that was discussed a bit in another thread, but I think that's less of an issue with coilovers in the rear. As transfer approaches 100% where does bending of the axle/tubes show up? Other effects like compression of the outboard tire need to be considered too.
     
  2. Mad Hatter

    Mad Hatter Gotta go Faster

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    This was our attempt to keep the rear wheels better planted... Unfortunately the actual bar broke after about 5min on the track so I could not get a good feeling for the changes... Mechanics Idea is to get the bar putting the inside tire down instead of up. I did get the impression that understeer was less then with no bar but that track only has one slow corner.

    Yes the car felt really planted in the long curve before the straight. Thanks for the pics!! Next event will be trying out the P2000 320/650-18 tires on 18x11 Apex wheels, Can't wait!!

    Most of the changes were things like spherical A arms etc so more or less I just need to get used to it with out wanting to undo it!! Was surprised to see how much better the car felt, was prepared to have a rougher ride but it did not happen.

    Definitely need more track time to get used to all the changes and see the improvements so enrolled myself for track classes again.



    [​IMG]
     
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  3. Grant 302

    Grant 302 OPM Spent: $587,402 Moderator

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    Neat looking bar, but I see the potential for bind in the ball joint/rod end (?) connection. Did one of those snap or near that connection?

    The bar would still unload the inside, and I think with this arrangement would make it a tad stiffer than the same diameter in the OEM location and connection style.
     
  4. Mad Hatter

    Mad Hatter Gotta go Faster

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    Yes, looking at the options now, was 15mm.... the bar broke just by the axle near the black support (just above the 90degree elbow).

    Its quite similer to the whiteline rear bar but much much thinner.... That one is 27mm
     
  5. Grant 302

    Grant 302 OPM Spent: $587,402 Moderator

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    Not surprising. Binding in that area will stop parts from acting axially in torsion and put some of it in bending. That's why the OEM bars aren't restrained much at the ends.
    Understood. Yes, except that the mounts are more outboard and will make the the bar for a given diameter relatively stiffer.


    I'm seeing more than ~1.43º compared to the rear wheel. I think the net is negative camber and it looks like it compared to the purple lines along the track width. Red is body roll for reference. Green for the rear, blue for the front.
    31144273_10215616696512962_5980397932799590400_o-2.jpg
     
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  6. Grant 302

    Grant 302 OPM Spent: $587,402 Moderator

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    Might help others see with the picture rotated a bit so the ground plane moved closer to horizontal in the picture:
    FullSizeRender 2.jpg
     
  7. twistedneck

    twistedneck TMO Race

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    Awesome thread. A few notes.. nothing new for these experts but maybe these help.

    1. Gain more traction out of the corner by using more rear spring and less bar. I.e. stop un weighting the inside rear wheel.
    2. It seems all the uber race cars sit lower in back than yours.
    3. You are throwing so much rate and damping at it.. im surprised to see that much roll and or pitch. Maybe its a very high seat position? Sitting more forward. Try burying the seat to lowest.
    4. Your diff could be biasing the rear wheels while braking. If its the eaton true track like mine.. unlike torsen these do not freewheel the diff on decel.
    5. Anti squat in rear means pro squat while braking. i.e. rear contribution to brake dive increases w increasing anti squat in the rear. (Hence desire to align the link level w ground)
    6. Springs first for frequency match front to rear and ride height.. then front bar to balance roll couple then final fine tune w rear bar.
    7. ..?
     
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  8. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    #5 . . . the braking side of anti-squat for acceleration is anti-lift, where the geometric effect is to allow a portion of load transfer to occur without the rear rising. Increasing the anti-squat increases the anti-lift, which decreases the rear rise under braking.

    I suppose you could think through this in "pro-squat in decel" terms, but you'd have to be referencing the "squat" as the amount downward from the rise you'd get if the anti-squat was zero (the anti-lift would be zero as well, and the rear of an S197 would shoot even higher upward than it already does). But I think the potential for confusion is a lot higher with this approach.


    #6 . . . is more of a street or dual-purpose approach, though I'm sure you can make it work to give a "more rear spring/less rear bar" configuration as long as you choose damped vibration frequencies appropriate to the use. Damping lowers vibration frequencies - and probably makes it less necessary to match them for flat ride purposes because increased damping causes the magnitude of the vibrations to decay more quickly.


    Norm
     
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