Neutral handling with low drag set up not producing good lap time

Discussion in 'General Discussion' started by cyrusyn, Jun 20, 2018.

  1. Andregee

    Andregee Registered

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    It is not my friend, I know the gentleman due to a setup course in which I have participated and this has cleared up with all these half-truths circulating on the Internet by self-proclaimed experts. And this gentleman doesn't believe anything, he simply knows it, he has studied the relevant topic with a degree and is now working in this area.And he doesn't claim that hard feathers basically mean more grip, the whole thing was deliberately limited to a flat track with the remark that a bumpy track needs a correspondingly softer set-up to keep the wheels on the track, whereby here of course the Fast Bump and Fast Rebound values of the dampers come to bear.The linked setup guide, on the other hand, says that soft springs basically mean more grip and that's simply nonsense. My knowledge of physics is also not so bad as not to be able to follow his arguments. It is essential to reduce the lateral inclination to a minimum so that the centre of gravity does not shift to one side, which is always associated with loss of grip and lateral inclination is reduced by stiffer springs and thicker anti rollbars
    I I also know very well how the shock absorbers work, they slow down the movement depending on the movement of the shock absorber. Of course they also exert a certain influence on the weight shift, but only while it is taking place. Once the centre of gravity has completely shifted, only the springs and stabilizers provide the resistance to prevent the vehicle from tilting further.
    Stiffer springs only mean less grip on a flat track and only on one axle if the stiffness of the springs is only increased on this axle. The reason is very simple. If the springs on one axle are tighter than selected, the vehicle will support itself more on this axle against lateral inclination during cornering, because the springs on exactly this axle offer more resistance, which means that exactly on this axle the wheel load difference increases, which just causes the outer wheel to gain less grip than the inner one loses, so that the axle has less grip than the one with the softer springs.As a layman, one could of course make the mistake that harder springs basically mean less grip, that they are mounted on an axle, e.g. the front axle increases the understeer, because the front axle thus offers less grip than the rear axle.
    However, this is only one aspect that has not been thought through to the end. If the spring stiffness on the other axle is additionally increased, the wheel load difference on the first axle decreases again, as the second axle then again increasingly supports the vehicle against the lateral inclination. This is also the reason why with the springs and anti rollbars the driving behaviour can be tuned in the direction below and override, one always changes the wheel load difference and the axle which has a smaller wheel load difference" offers more grip and If both axles are now tuned more stiff by stiffer springs or additionally thicker anti rollbars , the wheel load difference on both axles decreases due to the lower lateral inclination with the result of overall more grip
     
    Last edited: Jun 29, 2018
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  2. enduser

    enduser Registered

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    Exactly, the point is to have the car as low as u can , and thats where that guide is wrong, increasing suspension height is not neutral, it increases drag something thats implemented in rf2 as well as (optimum) rake angle.
    I m surprised/dissapointed rf2 doesnt have ride height telemetry or even an indicator for when u touch the ground, its basic stuff and important in any open-wheeler i believe. I know theres motec (3rd party) but i hate alt-tabbing and plugins that break with new patches, good thing its going to be in the new ui when it comes...

    @Andregee
    "The goal is as stiff and as deep as possible" doesnt mean the stiffer the better without any limits or else u would remove springs and dumpers for maximum stiffness! Obviously thats not the case.
    You posted as i m typing , what u need is the fastest weight transfer to the tires u can get but u already said that. So yea u need the car to be responsive and on the other hand real life tracks have bumps. Imagine a modern f1 car with high COG and soft suspension allowing for large body roll (ok thats not modern, its to make my point :)), in modern circuits trying to go fast by the time the weight transfer is done u would be out in the gravel/crashing.

    Apologies for my rambling.. one reason why modern f1 has a wheelbase from 3.5m up to 3.75m(!) for mercedes (looks like a truck lol) is to have heavy components as low as possible and close to the center of the car as well, u dont have additional fuel tanks left and right like in the 70s either. Front part of the monocoque is the thickest part for safety reasons but also its where the front suspension is mounted ;), rear suspension is mounted directly to the engine block so attention is given to minimize overall chassis flex.

    But you dont say what type of car the course was about, i dont believe top class open wheel cars allow for that kind of weight transfer u r describing anyway.
    Also the guide we re talking about is very basic one and oversimplified but a good starting point except for the suspension height thing.

    Back on topic , one way to increase responsiveness and corner entry is to increase front toe out, but bare in mind that u also increase tire wear so it may become a trouble in a race setup, in general i think its a matter of balance all around as in having to do the right compromises that work in your setup. Another important one is shifting weight balance slightly to the front with the same effect as above and again no aero change although u reduce rear grip so depending the car and setup the positive may outweight the negative changes (or the other way around) , the fastest setup is a slightly oversteering one ...if your delta lap time (this feature is gold) is negative ur doing something right simple as that.
     
  3. Andregee

    Andregee Registered

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    On an absolutely flat track, springs and shock absorbers would not be necessary and an absolutely rigid connection of the wheels with the body would be the optimum solution.

    The weight transfer from one side to the other has to be avoided as much as possible, so racing cars are also as hard and deep as the track allows because you will allways loose grip caused by it.What good is it if the outer tire gains 30% grip while the inner tire loses 40%?

    Thats out of context.

    The whole thing is a physical fact that occurs in every vehicle.
    The lower the centre of gravity and the lower the lateral inclination, the less the centre of gravity shifts outwards and the less the wheel load shifts outwards. And yes, modern Open Wheels are less affected by this phenomenon than the old ones. There is a reason why these are currently set much lower and are equipped with a much tighter suspension. Take a look at the suspension movements in Rfactor2 of modern open wheelers for comparison from the outside perspective. There is hardly any movement worth mentioning.
     
  4. Lazza

    Lazza Registered

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    Going off-topic for a second, new patches don't break plugins (it's possible for some, but very rare), and I wouldn't expect much telemetry in the UI for a while.

    @Andregee I did say 'if', and as you're not stating an absolute I don't have a problem with that. I think it's dangerous to make blanket statements about springs, because it depends on the track and springs don't act alone (on normal cars with dampers and ARBs etc). Setup guides tend to say that soft springs will produce more grip because A) it's usually about balance, rather than car performance overall, so softening one end, and B) most tracks have some bumps and spring softness will help with that. But a car with other suspension components and other factors such as significant downforce levels will need things other than springs adjusted, plus spring stiffness has some beneficial effects there (which a setup guide should mention in those contexts), so in the end it's all compromise. Most decent setup guides I've read don't say outright 'softer springs give more grip' without some qualifiers.
     
  5. davidporeilly

    davidporeilly Registered

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    So gents,
    I was intrigued by the debate about whether or not stiffer is faster. It called into question a lot of theory and it needed to be tested.
    We all learn by these debates but there needs to be some factual basis.
    I once worked in a company where we used to say " a man with an opinion and no data to support it is a man with an opinion".
    So test it I did.
    The test:
    Car:The Brand New Endurance cars from ISI have their latest tyre, I am testing and setting one up so that seemed a great place to start. I used the Porsche 911 RSR.

    Track: I used Nazareth Oval, short simple and tests mainly steady state cornering performance. Static rubber reperesentative of a rubbered track.

    The test process: I took the current evolution of my set up and did a test run. Then I increased spring stiffness symetrically until I was out of adjustment range. This way car balance would be unchanged. Then I did another test run with the stiffer car.
    Now with my eye in I did further runs with each and recorded the best lap time.

    Long stint test: Then I did a 10 lap run with each as fast as I could go to get some more data.

    here follows the data. Below you can see the setups. Stiffer one highlighted. Stiff vs soft sets.png
    Here follows the 10 lap run with stiffer springs
    10 lap run stiff.png
    Now the 10 lap run with softer springs
    10 lap run std.png

    The next slides show a motec overlay comparing tyre data from both runs (Pressure, temp and wear). The the back line is the stiffer setup.
    10 lap run pressures compared.png 10 lap run tyre temps.png
    10 lap run tyre wear stiff vs soft.png
    This slide is suspension positions.
    10 lap run suspension position.png
    Observations:
    1) Outright pace; the softer set was faster but not by much. Appr 0.118 sec.
    2) Consistency; the softer set achieved a lower delta of about 0.3 sec in most laps. Whereas the stiffer set was over double that.
    3) Tyre data; The stiffer set created higher temps, pressures and wear. The temps were especially high in the early laps when tyres were cold, later laps not as apparent. Wear rate on the FR was 20% higher. (95% vs 96% remaining after 10 laps).
    4) Suspension data showed less movement as would be expected. Suspension velocities were similar (no slide shown).
    5) Subjective observations; Fore-aft balance remained the same but the stiffer car moved around more, required more correction.

    Conclusions:
    The softer spring settings were faster, more consistent, easier to drive, better on tyre wear.
    The test and data does not support the theory that stiffer is better. The excessive heating and wear on the FR does not support the theory that stiffer springs equalise wheel loads.
     
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  6. SPASKIS

    SPASKIS Registered

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    Nice lesson David. I fully agree with everything in it. The way you did the test and the conclusions yielded.

    Too many people have theories but few actually try to put some scientific approach to prove their hypothesis.

    According to my experience the problem of excessive low stiffness is the laggy and sloppy behaviour due to the amount of energy that can be stored in springs. A stiffer car is more direct to drive.

    Dampers on the other hand don't store energy. They just induce some delay if too low.
     
    Last edited: Jun 30, 2018
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  7. Andregee

    Andregee Registered

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    If you use stiffer springs you have to adjust the dampers too, and to adjust the springs at the front and rear for the same value does not mean that that the car is still balanced because the different suspension geometry absorbs forces in a different way so a hotter front right tyre means nothing what could not be conpensated with stiffer rear springs and very important, driving on an oval track needs a complete different setup with positive camber on one side and so on. Let another Driver use stiffer springs and He will prove a completely different result and even if stiffer springs provide more grip, not every driver is capable to use it for better lap times. If you want to test correctly, use not an oval take a Flat track and use a soft springs with perfect balanced other settings and stiffer springs with the further perfect values
     
    Last edited: Jun 30, 2018
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  8. davidporeilly

    davidporeilly Registered

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    Well I was sort of expecting this type of response.
    In essence,The data didn't suit your beliefs therefore the test was wrong.
    -Yes it's an oval but it demonstrates perfectly cornering performance in a road setup. If I was doing an oval race I would do an oval setup, but I'm not, I'm testing a road circuit setup. "Positive camber and so on", where does it end? The possible combinations equal infinity. To get reliable data you change one thing. I tested stiffer springs as the only change-they aren't faster.
    -Needs a better driver who will prove you are right and get the results you want? Well going down that route of debate is tricky without it getting a bit personal. But I have done a lot of racing both in real life on real tracks and in simulations.
    The pure fact that the front right tyre is sliding/heating more and all tyres are wearing more PROVES there is less grip. End of debate.

    Feel free to carry out a test yourself to support your argument.
    Until then you are a man with an opinion and no data to support it.
     
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  9. Andregee

    Andregee Registered

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    That's not my beliefs its a fact of real racing engineers they are working with. If you think its so simple to get more grip by only adjusting the front and rear springs by the same value than you are totally wrong. A hoter right front tyre proof only one thing, the rear springs are still to soft so that the wheel load difference at the front is to high. Use stiffer rear springs and you will notice that the problem is gone
     
  10. davidporeilly

    davidporeilly Registered

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    Feel free to carry out a test yourself to support your argument.
    Until then you are a man with an opinion and no data to support it.

    You seem to think that you are the only one who refers to real world engineers and race engineering guides. You are not.
    I'm going to leave this debate now until you introduce some proper test data.
    I will even accept a link to some real publication etc, so far its some anonymous person who told you and your beliefs.
     
  11. Andregee

    Andregee Registered

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    Maybe you understand what you can read in the spreadsheet
     
  12. SPASKIS

    SPASKIS Registered

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    So a setup tuning teamspeak session in German with the same internet obtained pictures of fundamental vehicle dynamics throughout the whole video is your best support for your statement?

    At least It wasn't in Chinese...
     
  13. Andregee

    Andregee Registered

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    What's your evidence to proof the opposite?
    You should know, that a test with usefull results will take much time, first driving the car on a track so long that I reach the Best possible lap time for me, than driving a setup with soft springs but with adjusted values of the other components to fit to the springs an to get the fitting driving behaviour that it fits for my driving style and than the same for stiffer springs. That's not done like a few posts before with some clicks and a few laps
     
    Last edited: Jun 30, 2018
  14. SPASKIS

    SPASKIS Registered

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    If I do my tests and report will you do yours and post them as well?
     
  15. Andregee

    Andregee Registered

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    I am ill at the Moment, so I fear I can't really drive clean at the limit to show something usefully and no contantly clean laps would not help. Give me some days
     
  16. enduser

    enduser Registered

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    Forum fight is on?! :eek:

    Chassis flexing is not out of context, u dont seem to fully grasp what we re talking here, chassis flex moves cornering forces further away from COG and into one wheel only so its pretty relevant, i m also trying to say that such physics are well known in motorsports that in its ultimate incarnation (the most expensive one, f1) its taken into account from the very start of the car design.
    Ofc it applies to all cars, rally cars would like stiffer suspension, lower COG and whatnot, but in practice they maximize their grip in rough gravel courses with rather soft and tall ride. You forget that fine tuning adjustments are relevant (softness) and much more delicate than a generic sentence, that u always prefer as stiff suspension as u can and that www is full of myths (also very generic).

    About theory, when tuning a car setup u have moved on from plain theory and into practice and actual (or rather virtual in rf2) conditions.

    Theres a reason why most setup guides mention changes as oversteer and understeer , then go on to explain how to improve grip using examples in order to learn how to setup ur car in any track so that you dont go to albert park (just as u begin a season in f1 btw) and think soft suspension , soft dampers, remove ARB remove packers and say "grip here we come" or something like that.

    About theoritical flat tracks, ok u mount a theoritical suspension with made of material with of infinite stiffness and zero extra weight, similar imaginary chassis and u have all forces handled by the tires only. Tires then would deform much more , at first maybe u could increase pressure but they would also overheat and reduce their life span significantly so in order to last for a race of 3 pit stops u would need a harder compound... only to reduce grip , or u also have zero weight shift and car movement with tires without wear that hug the road at their full width at all times, no negative camber curves, no rumbles bla bla and suddenly im playing lotus turbo challenge. :p :D
     
    Last edited: Jun 30, 2018
  17. Andregee

    Andregee Registered

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    That the myth still holds, that softer springs absorb more energy and thus protect the tyres. So the overweight man who is afraid of his doctor goes to the doctor the next time with very softly soled shoes and the scales already show a lower weight,finally the thick soft soles absorb energy so that the weight is less loaded.
    Or even better, the fat man straps a few springs under his feet, preferably the very soft type.
    The springs transmit less force to the tires only for the moment of their own compression, when they are fully compressed under load, softer springs allow more lateral inclination than stiffer springs and this means that the centre of gravity shifts further outwards, putting even more load on the outer tyres than if the lateral inclination were to be prevented.
     
  18. SPASKIS

    SPASKIS Registered

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    Softer spring absorbs more energy. That's not a myth but a fact.

    For a given force F, the displacement equals x=F/k. And the energy stored in spring would be E=1/2•k•x^2= 1/2•F^2/k.

    Hence the energy absorbed by a spring is inversely proportional to its stiffness.
     
  19. Andregee

    Andregee Registered

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    Yeah, when bumps hit, but that wasn't the topic here. If i drive on a flat track throught a corner there is only a very short period of body roll aborb energy.
    Afterwards the springs are compressed accordingly and thereby transmit the full force to the tires. It doesn't matter how soft the springs are, if 250kg act on each of the outer suspensions starting from the body, then after compression the springs also pass completely to the wheels.
     
  20. patchedupdemon

    patchedupdemon Registered

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    I don’t know much about setups,isn’t it all about compliance,car track specific,transfer of loads etc.

    I don’t think blanket statements do any justice,like a stiff as possible,or soft as possible.
    Aren’t setups always a comprise,so the middle ground is more prominent than the extremes.

    Even on a flat track,compliance is key,so saying harder is faster may not be beneficial for braking and acceleration,but better for cornering or vicer versa,track depending you set it up for the important corners no,so your having to comprise and prioritise for certain elements of the track
     

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