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PHYSICS Bumpstop telemetry in the setup screen

Discussion in 'ACC Blog' started by Aristotelis, Oct 11, 2018.

  1. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    Yes you're right, I wanted to explain it, but was running around with the release, sorry. So:

    Yellow line:
    Suspension movement. Obviously the car is stopped at the box so no movement but this is where your suspension "sits". While driving, imagine the suspension line moving up and down. Up when the suspension goes into compression, down when it extends.

    Red line:
    Bumpstop (up) point. By changing the "bumpstop range" value (which we should better name it bumpstop gap), you modify the space between the suspension "free" travel (only springs) and when it touches or presses the bumpstop. The closer the red line goes to the yellow line, the sooner the suspension will start compressing the bumpstop and this raising stiffness and controlling the suspension compression movement.

    Green line:
    Just the end of suspension travel in extension. Not in scale, safely ignore.


    Small reminder; As you know by now, cars that have important aerodynamic features as splitters and diffuser, are quite pitch sensitive. That means that when you brake the car pitches forward, making the front splitter going closer to the ground and the rear diffuser going further up from the ground. The effect of that is that the aero balance moves heavily towards the front of the car. If this pitch movement is not constrained, the car can become very unstable especially under trailbraking turn in.

    How to setup the car?
    Rule of thumb (but as always your mileage may vary, it's all a compromise).
    The more stability you need under turn in, the more you need the front suspension to touch the bumpstop when pitching forward. So to make the car more stable, you need to lower the "bumpstop range" value so that the redline goes closer to the yellow or even touches it. Obviously if you need more turn in, then you go the other way around. You can also modify the stiffness of the bumpstop by increasing or decreasing the "bumpstop rate". Later on you it will be also possible to change the linearity. (note: rear wing can stabilize this effect too making it more mild and permitting a suspension with more gap until the bumpstop (or softer bumpstops).

    Generally you want less bumpstop work at the rear, so that the rear end absorbs kerbs and bumps and gives traction. Still, if the circuit permits it and driving style can handle it, you can do similar setup to the rear. Making the suspension touching the rear bumpstop sooner, you raise the stiffness and also limit the squat of the rear end, preventing the aero balance of shifting too much to the rear and limiting power on understeer.

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  3. so bumpstop range is the length of the bumpstop, so to say? does it have a unit? is it 10mm? 10cm or 10 what? we could to an analogy to those pro pedals you see, that you can exchange bump rubbers in different sizes and rates, harder, softer?

    Sorry for the silly question :)
    Last edited: Oct 11, 2018
  4. mkotechno

    mkotechno Simracer

    AFAIU in this text and it actually surprises me, bumpstop range is the space in which there is no bumpstop; so the higher the value the smaller the bumpstop is.

    I would recomend the devs to invert the value or change the attribute name because is hard to make a mental picture like it is now.
  5. Radfahrer

    Radfahrer Hardcore Simmer

    As Aris said above : " By changing the "bumpstop range" value (which we should better name it bumpstop gap), you modify the space between the suspension "free" travel (only springs) and when it touches or presses the bumpstop

    A bit of a misnomer there, but knowing Aris and his crew, they┬┤ll be changing that soon ;)
    Last edited: Oct 11, 2018
    Leonardo Ratafia likes this.
  6. Georg Siebert

    Georg Siebert Simracer

    it's 10 chickens
  7. TheMarshal

    TheMarshal Gamer

    I love this new setup screen. Great improvement!
  8. BrunUK

    BrunUK Alien

    African or European chickens?
  9. aotto1977

    aotto1977 Simracer

  10. Rehooja

    Rehooja Racer

    Keep these blogs coming! They are very informative and great read.
  11. Epistolarius

    Epistolarius Alien

    I'm confused about the colours. "Yellow" in the text is in orange. And the image has no red line. I assume it's the orange line?
  12. GRFOCO

    GRFOCO Alien

    This is great but, is there a way to view the entire graph of 1 complete lap?
    I mean not for now i know, but in the future, do the game will give us a tool to read "how much close the suspension goes to the bumpstop here and there"?
    A sort of telemetry, not realtime telemetry, but just something that record your last or best lap and can be read in the setup page, or when we come back to the pits.
    SimGuy_1, falkeGT and mkotechno like this.
  13. mkotechno

    mkotechno Simracer

    Just copy Gran Turismo 5 simple but effective telemetry viewer.
  14. Georg Siebert

    Georg Siebert Simracer

    The only ones you'll be able to afford to eat after the end of march.
  15. Ace Pumpkin

    Ace Pumpkin Alien

  16. flihp

    flihp Racer

    Quick question regarding this, I can see that adjusting the suspension/yellow on say left front, it also changes it on the right front. Is that due to softening or stiffening the suspension on one Front side also allows for some compensation in suspension compression whilst at speed on the other side, ( hope that makes sense); , also on the lambo, the yellow bar for the rear, stays extremely low, no matter on the setting, is this due to greater weight on the rear end?
  17. AC_RAF

    AC_RAF Hardcore Simmer

    @AC Support Can you put this thread in Sticky threads?

    I was looking for this (essential) information but it became difficult to find it.
    flihp likes this.
  18. LeDude83

    LeDude83 Alien

    The explanation in OP is excellent and - again - added value to ACC. It's like a car setup training when you could could just say: "Pff...I gave you the car, go figure it out for yourself."

    It will be very useful for me because I'm trying to tune the BMW suspension so that I can safely mount the right curb leading into Schumi S n N├╝rburgring. I see many other drivers taking that curb but for me, I usually end up slower when I try or even spin 1/5 times.
    I have the impression that the right suspension is kicked up a lot into the bumpstop. If I understand you well, @Aristotelis that's not exactly where you'd want to ride on the bumpstops, no? You'd want the spring and damper to do that work here, right?
    Noisen likes this.
  19. Aristotelis

    Aristotelis Will it drift? Staff Member KS Dev Team

    Under normal conditions yes, you want the spring and damper to absorb the hit.
    But if the kerb can make the car bottom out and the diffuser to stall, then you might want to stiffen the rear suspension to prevent this from happening.
    If you put very stiff springs, then you'll lose traction in all the circuit.
    But if you keep normal springs and manage to adjust the bumpstop to be hit only on that specific occasion, you can get best of both worlds.
    Warning: Everytime I try to do that I end up losing weeks with "now is aaaaalmost perfect but no"... LOL
  20. SimGuy_1

    SimGuy_1 Racer

    I did one experiment where i setup the rear bumpstop on audi at value 1.
    I don't know the unit.
    Do you think it's realistic to do so ?
    I did this to prevent power on understeer and it did solve little bit of it and my laptimes(hotlap mode) are not comprised.
  21. iVG

    iVG Alien

    There's a few other options to explore before setting rear bumpstops ranges so tight. Rear springs, rake, rear bump damper settings, front rebound.

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