Suspension ideas?

Discussion in 'Mustang Chit Chat' started by Cpjetmech, Nov 14, 2020.

  1. Pentalab

    Pentalab forum member

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    Correct. Which is why an adjustable PHB is used. The axle stays put, the rear end of the car body moves side to side. Pass side of phb goes to the body. The driver's side of the PHB goes to the axle. PHB needs to be shortened a bit... to center the car.
     
  2. jewc75

    jewc75 forum member

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    Strange single adj struts in the front, Viking Warriors in the rear, and BMR drag springs. Where you at in Texas?
     
  3. When addressing drag racing on these chassis’, the chassis will distort naturally and gets worse with increased power. These cars apply power unevenly in the rear when launching on prepped tracks with sticky tires. They are prone to the same torsional twist as older more inferior mustang chassis’. The car I was referencing wound up with 850rwhp aided by a 100 shot to get there. The launches were brutally high. My car has everything including an arb and my car leaves straight as a pin, I have 1” of body lift from the tire on both sides but this is almost impossible from stock components launching above 3k. My point is, when twisting the chassis from hard launching, these braces will flex in the middle and that’s where the 2 oem ones that we trashed were bent. That car is long gone though
     
    jewc75 likes this.
  4. jewc75

    jewc75 forum member

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    Im on a arb too
     
  5. Flusher

    Flusher Member

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    Air Locker?
     
  6. jewc75

    jewc75 forum member

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    Anti roll bar.
     
  7. Flusher

    Flusher Member

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    Thanks. Selectable lockers look kinda dainty, I would be suprised if they lived on the track.
     
  8. OX1

    OX1 forum member

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    Anyone done this with any success on a stock height car? I thought about putting them in for the track (1/4 mile), but could not find any info other than to correct susp geometry. Wouldn't mind a bit more bite on the street. I currently get zero wheel hop, street or track, with only Roush upper/lowers. If it would only work with adj upper and/or lower, than not really interested in going from the stiffer rubber to something even like delran. Primary objective of this car is still to keep it as close to stock NVH as possible (I've had plenty of cars I "ruined", and then didn't want to drive anymore).
     
    Last edited: Nov 20, 2020 at 3:23 AM
  9. Norm Peterson

    Norm Peterson corner barstool sitter

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    Two sides of the same coin.

    "Correcting the geometry" is mostly about axle roll steer and the car's understeer-oversteer handling balance. Lowering the rear of the S197 makes the rear suspension more understeerish than it already is (which isn't exactly terrible). The reason for going with relo brackets here would be to bring axle roll steer back nearer to stock.

    "Increasing anti-squat" is about improving initial launch bite, and what it amounts to is intentionally changing the side view geometry for that purpose rather than correcting it because you messed with ride height (which threw it 'off'). This works because load transfers more rapidly onto the rear tires through the rear suspension linkage's side view geometry than it can transfer through the springs (you have to wait for the springs to compress before their contribution to vertical load on the tires actually shows up at the axle). So the more the rearward load transfer you can force to go through the linkage, the less goes through the springs, and the better your launch bite gets. In the extreme, you can actually force so much load transfer to go through the linkage that the springs actually unload and the rear actually rises up. Sometimes called 'separation' ('body lift from the tire' earlier in this thread by sportin').


    There's a catch to how much anti-squat you should build in if it's a street driven car. It's possible to overdo things for the straight line to the point where the rear axle becomes oversteerish in nature, which can make for a rather unrelaxing (possibly "exciting" and not in a good way) drive.


    Norm
     
  10. Norm Peterson

    Norm Peterson corner barstool sitter

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    Trust me, after spending about 40 years as a structural analyst I have a pretty good idea about structural deflections under load. I'm still trying to picture how the brace could either be actively placed in enough bending from the two ends, or how it could be made to pick up enough load in compression to buckle. It'd be a lot easier to accept the possibility that a deep diff cover, the kind with the bearing support feature, could have been contacting the brace at some point.


    Norm
     
  11. stock diff cover. there were no contact marks. we just assumed that it was frame twist because that car had wayyy too much power and didnt have all the parts necessary to accomodate what we were doing with it. videoing the launches from both sides, there was a huge variance in body lift from both sides on both ends of the car. the car was planting the right rear alot harder than the left and the left front was coming up much higher than the right. a cage probably would've helped tremendously with this twist. my 07 doesnt do this at all but i also threw the book (and the wallet) at it and plotted my setup so it is predictable and repeatable.
     
  12. Doug Huggard

    Doug Huggard Junior Member

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    I've had really good luck with the bmr stuff as well. I've got their drag springs(about 1.5 inches lower than stock) , rear anti roll bar, lca w/brackets, uca w/bracket. Strange front struts and viking rear. Cut a 1.44 60' the other night with a 3v through a 5r55s and it drives great on the street!
     
  13. Norm Peterson

    Norm Peterson corner barstool sitter

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    Thanks.

    What year was the car that bent two braces?


    Norm
     
  14. Midlife Crises

    Midlife Crises Member

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    On my 2010 GT, to shave a little weight I removed my Watts link and installed a BMR adj. Panhard bar. I had to use a relocation bracket so the PHB would clear the Ford Racing diff. cover. This caused the PHB to contact the stock brace when the suspension collapses and made an awful racket. Took a bit to find the problem but the twisted brace and paint rubbed off the PHB gave it away. I put the Watts link back on.
     
  15. jewc75

    jewc75 forum member

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    My 12 bent the brace. I put one from an RTR and it makes a lot of noise. Panhard now hits it. Looking at options now.
     
  16. DieHarder

    DieHarder Member

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    What about using something like a Cortex or Griggs torque arm to deal with the torque issue?
     
  17. Sigma6

    Sigma6 Junior Member

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    I use some BMR throughout my car, spring, phb, relco brackets, lcas. Don’t really noticed any increased noise however I’ve a bit tone deaf too. It hooks really good for a street car. Still in 2 piece ds & stock uca, and stock sways.
     
  18. Norm Peterson

    Norm Peterson corner barstool sitter

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    The chassis is still going to twist regardless of how the rear axle is suspended. Driveshaft torque reaction from the front is carried back from the engine mounts through the chassis until it runs into suspension roll stiffness.

    That includes both front and rear roll stiffnesses, BTW, which gets into why you'd remove the front sta-bar and/or add a big "ARB" out back for the dragstrip (you're using a more rearward distribution of suspension roll stiffness to do a better job of re-planting the right rear tire, which wants to unload due to driveshaft torque the other way inside the pumpkin).

    Torque arms do have their fans, but it's apt to be more difficult to get high values of anti-squat without making the torque arm too short. The matter of brake hop (think rear wheel hop under hard braking) is much more closely associated with torque arms than with 3-link/PHB or triangulated 4-link suspension types.


    Norm
     
  19. it was an 07. Kenne bell 2.8 on with 100 shot. I’ve seen posts thru the years of people bending these braces also with the same scenarios and higher hp so it proves to me our case wasn’t an anomaly. Dallas was just a cheap bastard that wouldn’t spend all the money he needed to get the car to put it down consistently without tearing shit up. Rear ends were also grenaded from 5500k and occasionally higher launches. I’m curious though, if arb doesn’t control the chassis twist ( which comes from the driveline 1st) how does the twist not show up when wheels leave level front and rear when arb and shocks/struts are properly dialed in? I mean, coming from launching and the car driving itself left or right from tq to car leaving straight and driving straight tells me that this twist has been severely controlled.
     
    Last edited: Nov 21, 2020 at 8:48 PM
  20. Norm Peterson

    Norm Peterson corner barstool sitter

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    The way I'm defining "chassis twist" is not the same as visible body roll. Not directly anyway. Twist would be the difference between front body roll and rear body roll, and they are going to be slightly different. Not a lot in an S197, because the chassis is pretty stiff torsionally (so the amount of twist is low) and because there are no easy visible references for noticing this twist.

    I promise, only a few numbers. The S197 chassis has about 15,000 ft*lbs per degree torsional stiffness, and driveshaft torque might be 800 ft*lbs times 3.3-ish 1st gear times maybe 2.0 either in the torque converter if automatic or as an impact factor for the sudden loading of clutch engagement with a MT. So with around 5000 ft*lbs applied against a 15,000 ft*lbs/degree stiffnss, that only gives about a third of a degree of chassis twist. Too small to see with the unaided eye even if you knew to specifically look for it.


    Something must be happening locally involving the combined loadings of the LCAs, UCA, PHB, and ARB at much higher loads than the chassis was designed for. Purely speculation on my part at this point, but it's at least possible for some "elastic buckling" to be going on in the chassis itself, enough to then overload the brace but without leaving permanent deformation or distortion in the chassis as evidence. Even if an 'oilcanning' sound happened, you'd never hear it during a run at the dragstrip with both cars' engines roaring and you with a helmet on (and possibly earplugs as well).


    Norm
     
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