This is why you don't run stock suspension...

Discussion in 'Road Racing Forum' started by domesticpower, Jul 28, 2019.

  1. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    Total roll stiffness does go to hell in a handbasket as soon as you lift the inside front and all you're left with is the rear suspension roll stiffness. But he has to be getting pretty good forward bite and as long as there's a net gain it's what you have to do regardless of what it looks like.


    Norm
     
  2. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    I'm putting "looks too much" squarely against the credibility of the person making that comment . . . or to the extent that there might be an agenda behind the comment. I suspect that fewer people actually identify the time element on their own.

    Agreed. For sure in any dual-purpose car even though you're still likely to end up with a firmer setup than what most people would be comfortable with.


    Just so you know, I used to do various forms of dynamic structural analysis back in the days when I had that thing called a day job. Always a time or frequency element involved. And I'm either fortunate for having a wife who's been more than tolerant about cars getting their suspensions stiffened. Either that, or I got it right by starting out really early in the program. One of her favorite cars was this one.
    Pinto3.jpg


    Norm
     
    Last edited: Aug 8, 2019
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  3. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    No need whatsoever for apology.


    Norm
     
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  4. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    Probably, but maybe not. Like Rob pointed out about "I think you will find that the shocks are going to be key..." The basic setup could be the same for you both, just adjusted differently for the specific use or course.

    Yes, but that relative to the course. I don't think of any Mustang or any V8 as being a momentum car regarding AutoX.

    Absolutely right. But putting a hole in the ear of the LCA axle side bracket really doesn't appeal to me. The stock parts, not the bolt ons. The chassis side UCA just doesn't have a lot of space to work with.

    Depends. If the actual roll rates 'match' for given conditions... they both come up.

    Agenda is one aspect...

    Identifying is one thing, but understanding is really difficult for most.

    This video from Engineering Explained is about spring rates...but (IIRC) he completely ignores damping here:
    What's The Best Suspension - Soft or Stiff Springs?

    I suppose one problem is many who watch such videos think they understand what's presented and that the conclusions must be true.

    Triple Friction Pendulum Seismic Isolation- Makes the dynamics of a race car suspension seem simple, right? ;)
     
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  5. ChrisM

    ChrisM No bad days.

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    You're just stringing words together. That doesn't mean anything!*

    *Clearly I am not an engineer.
     
  6. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    Thanks, Grant.
    Domestic's (OP) car has something like a hundred more ft*lbs available than I expect to ever have in mine, and is running at least as much axle gear as the 3.73's I'm about to be working with. I'm sure I could run the same geometry and stiffnesses as the more powerful car, but my question is whether there'd be any advantage in doing so. I have this vague feeling that running more 'anti' than necessary might not be the way to take a dual-purpose car.

    The possibility of coming up with some way to make fine adjustments where Ford provides no adjustments at all and the aftermarket only offers coarse adjustability is not off the table.

    Understood. For a few years I autocrossed a V8 car that was less suited to either autocross or momentum driving in general than the S197. It wasn't nearly as close to stock as it may appear. The cone with the pointer that I'm really wide of was a cone placed to intentionally suck you off line.
    85CP at Ripken with meaningless cone.JPG
    These days I'm only running HPDE, looking for a little success at the driver mod (or at least the hope of staving off the eventual driver de-mod), and as my own chassis guy and crew.


    I think it's the right side LCA bracket in particular that defies ever doing much in the way of modification without doing at least a little "hot work".

    Right now, the rear of my '08 is lowered by only about 5/8", and I've always wanted to drop the LCA pickup points a little for even that small change (mainly to move the axle roll steer back where it was - closer to neutral). Seems to me that welded-on relo brackets would constitute good reinforcement for putting new holes anywhere I'd be likely to want them to be. I may still raise the rear of the car up another quarter inch, which would take any proposed LCA pickup point with it.


    Just thinking about that . . . yikes!!!


    Thanks for the link. I've watched a few of his other videos. I used to do a lot of technical review work actively looking for things that weren't clear, outright errors, and miscellaneous oversights and disconnects in calculations and documents prepared by others.


    Certainly true as far as most forum-level discussions that basically work out of Millikens' RCVD are concerned. I might still have an educational copy of CarSim on some computer (never did do much with it, haven't touched it in years, maybe I should have), and that's a pretty basic program compared to Adams (an OE-level software that I don't know anything else about).

    Pretty sure I know what that Triple Friction thing is about even though I worked in different industries. Most of my involvement with seismic loading was with response spectra and various levels of structural damping.


    Norm
     
    Last edited: Aug 9, 2019
  7. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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  8. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    Like a million monkeys banging on a million keyboards. You must be new to TMO too! Welcome, @ChrisM !

    ;)

    I think you misunderstand me a bit...I'm thinking his car could run rates more like yours. Plus some of the other geometry mods we've been discussing. I don't see a lot of aero mods or takeoff slicks on his that would preclude you both from running very similar setups.

    I know what you mean, but the peak torque specs aren't that far off. Either will be limited by suspension regarding ability to corner exit.

    Sounds good to me.

    Exactly. Not something I want to do to either current car, but maybe my vaporware V6 project.

    Understood and agreed. I like the thought process on your setup and wish the aftermarket would produce something more along those lines. It's all that's really needed to make a great handling car that can run larger tires or better compounds. Panhard relocation and maybe some other front end tweaks that I like for better camber gain are a couple of other areas I'd change on a very slightly lowered car.

    I've done essentially the opposite. Everything in the rear is 'designed' around the available LCA adjustment points between 2" and 4" lower. And the stock panhard location.

    I just threw that out there because it was probably the most interesting structural element that I worked with...and it sounded like you worked with structures of some sort. And it was one of the few times I had to think about damping at work.

    I believe it! It does explain why I've thought to ask you to 'review' other technical posts and comment.


    :D
     
  9. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    Completely missed your intent :( . I think I know why, but that's way too far off topic.


    Thanks. If I wasn't an engineer I'd probably regret the time I've put into trying to understand this stuff beyond "if this, do that". I'm apt to throw problems like this one at Excel (I was still editing this one this morning).
    3LinkPHB V00L00.jpg

    J&N Performance started out about 20 years ago as an inside joke between me and my son.


    Norm
     
    Last edited: Aug 10, 2019
  10. DocB

    DocB TMO Advanced

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    @ blacksheep, these questions are in regards to that I was always informed that 4 tires have more grip than 2.

    In reference to the posted picture, don't you think you would get better rear traction with 2 rear wheels on the ground?
    And, since the car is still tracking out, wouldn't you get better lateral grip with 2 front tires on the ground?
     
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  11. blacksheep-1

    blacksheep-1 TMO Addict

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    here's the big problem with all that theory..
    the car was consistently faster this way, sometimes you have to take the bull by the tail and face the situation, in this case ..
    Just follow the lap times.
    Pretty much in every case, forward grip was faster than sidebite, there is of course a limit out there someplace, you can't get fast lap times if you can't get on the gas. This is why I've stated before "it actually is possible to over tire a car", probably not a mustang or high hp car, but one of the little turdhopper cars, you absolutely can do it. I've seen it done in everything from karts to autocross cars running open tires. I was taken to task for it but when a guy name John Heinricey confirms it, I'll go with him.
     
    Last edited: Aug 11, 2019
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  12. Coz

    Coz TMO Race

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    I guess this means the laps with the highest G-forces weren't the fastest.

    Reminds me of a boss many, many years ago that would always mangle sayings. One of my favorites was:

    "You have to take the bull by the tail and look it straight in the eyes"
     
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  13. blacksheep-1

    blacksheep-1 TMO Addict

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    ^^^ true, sometimes you do
     
  14. Fair

    Fair Go Big or Go Home

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    Respectfully... I don't care how many times you post that pic, or the fact that it was on pole, that 3 wheel motion image is not "dialed in right". That might work for that driver who has to use a LOT of curbing to defend to stay ahead of others, but that's just all kinds of wrong. The fact that you keep posting that is doing the community here no favors.

    [​IMG]

    Just like this super soft OEM spring setup is far from ideal. I saw this massive brake dive pic and saved it, either from here or Facebook. It was a pretty good one! That's the kind of thing we want to avoid, and it made for a great example for one of our constant contact emails. I honestly couldn't remember where I found it, but I will give credit to "Rams Eye The Track Guy" or "domesticpower" or whatever else he wants to go by. :) And photo credit goes to Kevin Doubleday. Yes I removed the blue tape "08" from the door, because it looked like a 5 year old made the numbers. ;)

    [​IMG]

    I was actually looking for this pic that my guys took at an event a few years back, of another boss that was one of my customers. With over 90K images on our server it was hard to remember where it was. ;)

    Glad the discussion of bad setups continues!
     
  15. blacksheep-1

    blacksheep-1 TMO Addict

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    Oh, it absolutely is "dialed right in" and the fact that Roush, Multimatic and everyone else running those cars ran similar setups in IMSA, PWC and other series successfully, proves my point.

    [​IMG]

    [​IMG]
    here's a poster full...
    [​IMG]
     
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  16. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    @Norm Peterson Not sure what's off topic in this one. I do understand why most wouldn't think that *I* could recommend rates you're using for the OP's car.


    Just to confirm, your Rollsteer chart is a dimensionless degreeº/degreeº vs. ride height? I would think this would be a 3D chart including ride height, or a 2D chart with curvature for a single given ride height. I don't think of roll steer as a linear property.
     
  17. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    Nah, Rob...that's just monkey-see-monkey-do, right? ;) :D
     
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  18. blacksheep-1

    blacksheep-1 TMO Addict

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    First off, my comments here are not a reflection on AJ, Joe, or anyone else at Phoenix, they can speak for themselves, and have no problem doing it, that being said, besides my working with them, I have been doing this stuff since I was 12 years old and could sneak through the hole in the fence at Sunshine Speedway. I would NEVER bad mouth someone else's setup or products, it's way too hard to make a living at this business if everything goes perfectly, and all your drivers are Mario Andrettis. That's while you'll never see me call out a product on here, Not Steeda, Cortex, BMR, Vorschlage or anyone else, I will never do that, they all build quality components. I simply offer a different perspective.
    This sight is becoming a very important for any mustang enthusiast that is the least bit interested in tracking their cars, I don't know what the numbers are but I would not be surprised if this page is not a player in the grand scheme of things. For this reason, I try to keep things civil.
    With regards to setups, there have ALWAYS been 2 schools of thought, back before the advent of decent coil over shocks,, in the 70s we had 2 guys, Bill Mitchell and Dick Guldstrand, DG used to have his cars flat and level, very little body movement BM on the other hand was, kind of "screw this" this car has to follow the road, he ran the lightest springs possible and did all the tuning using sway bars, both cars were fast, both won races, the big advantage was that you could take BMs cars to the track and start running competitive lap times by the second session, with DG, the car had to be constantly screwed with in order to make all the parts run in harmony with each other because each minor adjustment effected everything else. Mitchell's stuff, just didn't seem to care. Now that all these cars are built around the shocks the same holds true. The fact is, that none of our cars compete in any series that you (Terry) are involved with, and there has never, to my knowledge been a head to head confrontation, and even if there was, on any given day there is no guarantee of which would be faster..
    .In short. you guys spend your money
    our guys spend theres'.
     
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  19. VoodooBoss

    VoodooBoss Rick Moderator

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    Wow this one spun out of control fast. Not sure why but let's keep it on point. There are more than one way to setup a car so let's be respectful of that.
     
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  20. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    There was a reason I missed your intent, and that reason is irrelevant here. Hell, a couple of weeks on, I'm not even sure what it was any more.


    Yes, It's worked up specifically at 0° roll. If nothing else, that's where it starts out when the car begins to roll, and hopefully the small angle assumptions apply up to about 3° of roll (hopefully nothing varies too far away from linear).

    I get that roll steer would be a 3-D surface map. I've thought about it, but just never put the time into struggling through the geometry where the LCAs would be at different inclinations from one another.


    Norm
     
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