Help me choose a suspension setup

Discussion in 'Corner Carver Racing Tech Discussion' started by Screamin_dutch, Dec 12, 2018.

  1. Racer47

    Racer47 Doesn't have much to say S197 Team Member

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    I cut them down, more than half is cut off, something like 40% of the the original height remains. Then I ground down the top to make it cone shaped so it still has a progressive rate. Plus I used bump stop relocation brackets to move them more forward so it has more vertical clearance. The rear end really has a lot of potential travel.
     
  2. JJ427R

    JJ427R forum member

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    47, I as well have the Roush suspension, which lowers the car 1", and obviously suspension/spring rate is going to make a difference in how the car handles with these. Your springs are obviously way different, I'm not sure what the Roush are rated in lbs, compared to yours. I'm also not sure of what the difference would be with just the jacking rails as I have the Matrix Brace as well. Like Pentalab stated, it's kind of an apples to oranges comparison. On my car as well as Pentalab we noticed considerable difference in handling.
    And yes with my 10 years of experience I'd love to compete against you on the track if you want to come to Road America or Brainerd. I'll be at RA July 5-7.
     
  3. Norm Peterson

    Norm Peterson corner barstool sitter

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    My point was that if you're looking at the car's orientation against an imagined true vertical, 2° true roll because the road is cambering 2° out from underneath the inside will look like 0°. Tends to be misleading if you're not paying attention to the actual ground contour.



    Perceptions can be misleading. I'm not trying to claim the you and JJ aren't noticing anything, only that you're not assigning crediting where it belongs.


    "I suspect that any increase in stiffness (esp torsional) may well enhance the effect of the front sway bar."



    No. Increasing chassis stiffness does not change the front sta-bar from being responsible only for your left front corner to the whole left side. But for it to suddenly take over the entire left side's load transfer that's resisted by the bars, you'd have to disconnect the rear bar. And then you'd be seeing more roll rather than less.

    In actuality, the front bar is only providing one of the resistances to body roll, and the way load distribution works is that it divides up according to the relative stiffnesses. It's a springs in series/springs in parallel situation, where the stiffness of a reasonably stiff chassis plays only a minor role.



    I really don't want to get into finding areas and torsional resistances when the S197's basic chassis really doesn't leave much flexibility for them to help resist. Compared to the existing S197 main structure, these are small elements in a secondary structural role.

    The stiffness that they do add is far more effective at changing structural vibrations, which is something that does lead itself to being felt. It should make sense that a car that feels more solid is one you trust better and are more readily willing to drive harder.



    It takes more than the simple fact that they're present. It's how much additional stiffness they provide compared to the basic S197 chassis stiffness that really matters. It's the numbers that matter here, not the words.

    The addition of the CM jacking rails appears to be the final missing piece of the puzzle.... now tying the rigid front end....to the rigid back end of the car. The entire affair is pretty damned rigid. You folks can call it placebo effect, confirmation bias, pseudo junk science, or anything else you care to. [/QUOTE]
    Stop. Just stop. I'm trying to teach something that I think I'm still reasonably qualified to talk about.

    I'm sorry if I can't seem to find the approach that would really make this structural and mechanical engineering stuff 'click' for you. But if I didn't have a pretty firm grasp of the concepts myself, I wouldn't have been able to make an engineering career using them that spanned 42 years.

    I am not among those who might be calling this a placebo effect or anything subject to confirmation bias. I'm looking at this in a strictly objective manner as far as the structural and mechanical effects are concerned. And I know a little about what makes for a more confident driver, or conversely that a driver whose car provides a less secure subjective feeling just isn't going to drive it quite as hard. It may not take much to go from less secure to more so.


    Norm
     
    Last edited: May 15, 2019
  4. Pentalab

    Pentalab forum member

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    Roush springs are only 20% stiffer than oem, maybe 150-165 range..and that's the fronts. Jacking rails are one thing, but the welded in, full length SFC's from BMR, or the kb's matrix brace is another level.
    My fronts are still off the ground before the rears, if jacking in the middle.

    Norm, I have no other logical /technical explanation for what I'm seeing. I've run out of ideas.
     
    Last edited: May 16, 2019
  5. 759-OR

    759-OR Junior Member

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    47, thanks for the feedback on bumpstop. Tell me the purpose of the relo brackets. Were the stops missing the frame after you cut them short? And was that a custom piece you made?

    I’m not wading into anything else here. My rails are one of my favorite accessories. Just because it makes service way easier.

    ;-)
     
  6. Pentalab

    Pentalab forum member

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    Racer47, what brand of jacking rails did you install ?
     
  7. Racer47

    Racer47 Doesn't have much to say S197 Team Member

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    As far as I know Vorshalg is currently the only one making them. https://vorshlag-store.com/collecti...ts/s197-mustang-axle-bump-stop-relocation-kit The intended purpose is so that you can cut off the chassis bracket to fit wider tires. But they also move the bumpstop forward so it hits higher in the A frame above it. I was originally going to make them, since its just a plate, but I happened across a set for half price and just bought them instead.

    Steeda

    How is it possible for these to add enough chassis stiffness to be noticeable? All it is, is a filler tube that extends just below the pinch weld to make it easier to jack on. The front plate is even all cut up for the steeda logo. The rear bolts are on another plate. The actual square tube is not rigidly mounted to the car, just the plates at the ends.

    5555209_3.2727.jpg

    5555209_1.2727.jpg
     
  8. Racer47

    Racer47 Doesn't have much to say S197 Team Member

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    not stiff.jpg This is the weak spot. How can these 3 tiny areas of metal do anything for chassis stiffness?
     
  9. Norm Peterson

    Norm Peterson corner barstool sitter

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    Belated appreciation for your comments, Racer.



    This topic may have me revisiting one or two formulas in the spreadsheet I've been using. I expect only minor changes will result, none of which will reduce the average amount of body roll but will probably make the calculated amount of chassis twist a little more sensitive to changes in torsional stiffness. Won't be overnight, though.

    These rails probably do a better job of increasing the bending stiffness of the main chassis rails along the door opening than anything. Your seats would be benefitting from slightly firmer support at least at the outboard seat mounts, and I'm pretty sure by enough to feel.


    Norm
     
  10. Pentalab

    Pentalab forum member

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    Those end plates just hold the 2" x 1" rect tube in place. In my case, I had previously installed the steeda tq box triangular braces yrs ago, bolted and welded into place. ( https://www.steeda.com/steeda-mustang-frame-rail-torque-box-brace-555-5551.html ). The aft end plates of the steeda jacking rails slide between the upside down channel steel, that forms the 3rd corner of the triangle..and the under-body. I only welded corners #1 + #2 yrs ago. Damned good thing I didn't weld corner #3 at the time, or there would be no way to slide the aft end of the steeda jacking rail plate in there. I would have had to cut it off in the bandsaw...then welded the aft end of the steeda 2" x 1" jacking rails.

    With just the pair of bolted in steeda jacking rails by themselves, there is probably minimal increased chassis stiffness. But I added the rails...after the fact. Used in conjunction with the welded in tq box braces, I could tell the difference right after the install, something sure as heck changed overnight. I'm still not done with it. The plan is to weld each 2x1 jacking rail in 4-5 places along it's entire length, on the inboard side of course.

    Steeda shoulda just made the rails full length, but they made em shorter, to be used in conjunction with their existing tq box braces. That combo works pretty good, but still pales in comparison to a pair of BMR full length, dual rails, which requires a lot of welding....ditto with the KB matrix brace. For serious track
    applications, the BMR / KB would be ideal, albeit more weight / expense /sanding / grinding / welding required. http://m.bmrsuspension.com/?page=products&productid=191 https://www.bmrsuspension.com/siteart/install/SFC011.pdf
     
  11. eighty6gt

    eighty6gt forum member

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    nothing I like better than visiting threads like this watching people add to the mass of their car and subtract from the mass of their wallet. It's like that time I bought a $700 throttle body!
     
  12. Norm Peterson

    Norm Peterson corner barstool sitter

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    For serious track applications you really should go with a cage instead. Or possibly a cage in addition to some sort of undercar bracing.


    Norm
     
  13. Vorshlag-Fair

    Vorshlag-Fair Official Site Vendor Official Vendor

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    Very good observation!

    [​IMG]

    The hubris is amazing - when companies spend a lot of time to cut their logo completely through critical load paths on parts that supposedly "add stiffness" or otherwise have high loads going through them. I've seen control arms fail - at the logo. This silly part will fail - at the logo.

    "Luckily" this is just another "steelitus" upgrade, where you "throw steel at the car" to fix some perceived problem, but it does nothing but lighten the wallet. ;)

    Stay skeptical, people!
     
  14. Pentalab

    Pentalab forum member

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    I agree. The laser cut logo is a dumb idea.....(but good enough for jacking purposes, and to say it's a... 'bolt in mod'). For a more robust install, the 2x1 rect tubing itself should be welded in 3 places. Each end ......(and the middle, where steeda welded in a 2x2 re-enforcing / backing plate).

    For folks that have the steeda trunk mount 'X' brace, it too requires welding.... on all 4 x corners of the 'X'....esp the bottom corners. Unless the bottom 2 x corners are welded, (where they sit over top of the rear shocks, directly on the shock towers), they are doing nothing. As is installed per steeda directions, the tops are bolted, with 2 x 12mm bolts each, and each 3rd top hole is used for optional welding...for more rigidity. They don't mention anything about welding the bottom 2 x corners. As is, they are only held down by the nuts + rubber grommets. Fortunately, there is no logo on any of the 4 x corners.
     
    Last edited: May 17, 2019 at 4:34 PM
  15. Norm Peterson

    Norm Peterson corner barstool sitter

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    I'm not a fan of cutting a logo where strength is needed. Not at all.

    Though I do understand a vendor adding something to his design to discourage unauthorized parts reproduction, which I'm pretty sure the logo was intended to accomplish.


    Norm
     
  16. oldVOR

    oldVOR forum member

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    759-OR for the DIY'er What have you done to your mustang today?
     
  17. Vorshlag-Fair

    Vorshlag-Fair Official Site Vendor Official Vendor

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    [​IMG]

    Most people do not need to relocated the rear bump stop bracket. We did this on our Mustang (and many since) to make room for an 18x12" rear wheel, which we ran from 2012 through the end of of 2015 when we sold the car. Our unique wheel offsets allowed us to fit this massive rear wheel under the stock fenders using a 315/30/18 Hoosier, as shown above. We ran an 18x11" on the same sized Hoosier up front, also under stock fenders. Those were both "max fitment" race wheel setups under stock fenders.

    [​IMG]

    This 18x12" rear doesn't just "bolt up" without any modifications, of course. For 95% of the customers that want "max fitment" wheels on the S197 under stock fenders we supply an 18x11" rear instead. Even those still need an adj Panhard Rod or Watts Link to make sure the axle is perfectly centered.

    [​IMG]

    Ignore the AST shocks above - we quit selling those in 2012 - but the pic has good labels on all of the bits we are talking about. For that more dedicated 5% that wants every inch of wheel possible, we warn them that the inner barrel of our 18x12" wheel will "hang" on the upper tie-down hook/bump stop landing plate shown in the yellow circle above. Not a huge deal, never happens when driving, but it will hang up when you have the car in the air on a lift with the rear suspension at "full droop". To remove the wheels when the car is on a lift you have to put a jack under the axle pumpkin to raise it up enough to "un-hang" the 18x12" wheel barrel. This is annoying, but we have a way to remove that protruding section of sheet metal, shown below.

    [​IMG]

    After marking and center-punching about 12 spot welds, these are each drilled out with a spot weld cutter. Then this stamped sheet metal upper bracket can be removed, and our 18x12" wheel can fit at full droop without interference. Some folks leave the lower section (that follows the curve of the frame rail), to have some additional strength there - just cut it off at the corner and leave that lower bit spot welded on. We spray all of the bare metal exposed by removing this bracket with "self-etching zinc primer", which is often this drab green color. You can cover that with prettier paint if you like.

    [​IMG]

    Of course when you remove that upper bracket, the axle mounted bump stop no longer has an upper contact plate - which is needed to prevent "over travel" of the rear shocks under an extreme rear bump travel situations. So we developed this S197 rear bump stop relocation bracket kit, shown installed above. We always cut that bump stop in half on lowered cars, by the way.

    [​IMG]

    This kit consists of two CNC cut pieces of steel plate, powder coated black, and the hardware to mount the bump stop to the bracket, which moves the bump stop inboard by over 1/2", to line up with the beefy flat portion of the rear frame rail. The two stock bolts and captive nuts on the axle are re-used to mount the bracket to the axle. Simple, no welding required, and the first few we hand made have been in use for 7+ years without issue. We started selling production cut versions of these last year and have sold dozens - which we make in-house on our CNC plasma table, so we can't run out of stock.

    Cheers,
     
    Last edited: May 18, 2019 at 1:03 PM