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

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

  1. SPASKIS

    SPASKIS Registered

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    Every time they get compressed and extended, not only in bumps. While turning they also work.
     
  2. Andregee

    Andregee Registered

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    Like i said, for a very short moment of the body roll, that moment where you can feel a more spongy or directly, more precisely car behaviour. After the spring compression, the much longer and more important time while cornering, they give all forces further to the wheels or want you to tell me that I weigh less if I stand on a scale with springs under my feet?
     
    Last edited: Jun 30, 2018
  3. Andregee

    Andregee Registered

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    Even during braking or acceleration, shifting the centre of gravity can have a negative effect, as the rear axle is relieved during braking and can therefore transmit less braking torque. An unloaded front also has a negative effect on a front-wheel drive car when accelerating, but not on a rear-wheel drive car, that should be clear. In this respect it can make sense to support the weight shift backwards during acceleration if the grip on the rear axle is missing. In this case the slow bump settings of the dampers are used, in the example of the missing grip at the rear axle when stepping on the accelerator pedal, the slow bump value at the rear axle is increased, so that the shock absorber offers more resistance for the moment of accelerating and loads more pressure on the rear axle faster and not only when the spring has compressed itself accordingly.

    And of course, everything in setup is an compromise, the Callaway Corvette for example is so stiff, that its really difficulty to drive it on bumby tracks, the GTE Corvette is much smoother and you will never find a completely flat track i think, but to think hey i use the softest spring setting to get the most grip is not correctly
     
  4. ebeninca

    ebeninca Registered

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    Using Green track isn't a good idea. Because when you get Rubber you gonna have more grip, meaning you can use less downforce.

    Probably you're losing some lap time because of this.
     
  5. Jebstone

    Jebstone Registered

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    remember that time the OP asked for some help with tuning, and now it's become this?
     
  6. Korva7

    Korva7 Registered

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    If the car has high cog and soft suspension the lean of the car in corner can make the cog move closer to outside tires, increasing the load transfer. So i agree with Andregee that in the theoretical and simplified situation of being in corner on totally flat track, car with stiffer suspension should have more grip.
    Thought, most of the load transfer is not caused by the movement of the cog, but by the torque you get from the acceleration force pushing cog towards out side of the corner. And siffer suspension doesn't have effect on that. Unless the stiffer suspension allows you to lower the car and it's cog reducing the torque.
     
    Last edited: Jul 1, 2018
  7. stonec

    stonec Member

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    The setup guide I attached was supposed to give a simplified guide to operate for a beginner, which to me sounded like the OP was. Of course not every word in it will apply exactly under all sorts of conditions. Even on the next line in the same section it says "increase grip on bumpy surfaces", so it should be more or less implicitly understood what they refer to. If they would delve into every possible scenario each section would take several pages.
     
  8. Daniel Surace

    Daniel Surace Registered

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    People need to understand this is always a compromise when setting springs. And suspension geometry for some cars is different to other cars. A race car is relatively stiff compared to a road car so the talk of soft is really still stiff.

    It's always a trade off. And what balances the car better. Take the gp3 2018 car as an example. This car has a lot of understeer. If you take the car around a skid pan. Which I have done extensive testing with. You will see that a a soft car around there is understeery and heavy on Tyre wear. But once you use the springs to adjust the balance you start to find a stiffer rear makes the rear slide more which in turn loads the front alot less which lowers the front wear and ultimately a lower and consistent lap time. Now if you stiffen the front that balance goes away and you start to loose that affect of the car rotating resulting in slower laps and more wear on the front again.

    So people need take this into consideration. Really it's about what gives your car the best balance to produce laptinme there will always be a point where to stiff is too stiff and too soft is too soft. It's pretty black and white when you find that point. But you can't simply say a soft car is faster or a stiff car is faster it's simply relative. If you are to generalise a softer car always more contact with the road but doesn't mean faster.

    I'll see if I can find my telemetry log of all my testing with different suspension sets. The lap times around skid pans are like 13seconds so it's the quickest way to dial a pass suspension in for a car.

    Cheers
     
  9. Andregee

    Andregee Registered

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    Yes a deep cog helps allot the the increase grip and yes, a deeper cars needs a stiffer suspension to keep the car away from the ground.
    And of course modern racing cars are already tight even in the softest setting, so that the centre of gravity does not shift so much that it makes no big difference if you choose softer or harder springs that fit all around on flat tracks. And it might also be possible that a driver prefers softer springs even if they offer less grip and he its even so faster.
    In the end, all I wanted to say was that softer springs do not generally mean more grip. If someone is looking for the last tenth on a fairly flat track and still has room to soften the springs, he might get the idea that he simply needs to choose softer springs to get more grip and speed and that's not true.
    I testet it shortly for myself with the M8 on Spa 1.4 and was able to drive 0.45 seconds faster with the stiffer setup. Ok i was not in the best condition and yeah there where a few corner where i was faster with the softer springs, but that was caused by my own inconsistence but over the whole lap i was always faster with the stiffer springs. I drove the last laps with the softer springs so i had more practice, bevor that i changed back and forth and was 0.8 seconds slower with the softer setup. I will proof it with clean laps when i am healthfully.
     
  10. patchedupdemon

    patchedupdemon Registered

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    So will stiff shocks be faster at a flat track that only has very slow corners
     
  11. Andregee

    Andregee Registered

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    You mean dampers with shocks? Than Generally no. You can adjust the under or oversteering with the dampers and slow bump and rebound settings while weight transfer. Simple higher bump and rebound settings are not faster because you don't know how the car handles with that. The settings have to fit to your driving style.
     
    Last edited: Jul 3, 2018
  12. Ozzy

    Ozzy Registered

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    I like this discussion but people often manage it to disagree, when they actually somewhat agree with each other. :D
    @Andregee is totally correct when it comes to: stiffer = less weight shift = more equal tire loads = more grip because of load sensivity.
    I think the missing link, why davidporeilly's results don't show this, is the contact patch. In reality as in rF2, the overall resulting grip is not only a result of the tire loads, but also of the size and shape of the contact patch area (and probably more). I'm not 100% sure, but surely someone will correct me if I'm wrong, but rF2 actually calculates the specific load on many points of the contact patch. So more area + even load on the contact patch should result in more grip.
    So the test result could also show, that when changing stiffness without changing camber, dampers, etc. to componsate the change of the contact patch area, one will suffer in overall grip. (This assumes the setup was correctly adjusted for the initial spring settings)
    Would be interessting to see this test with adjusted camber.
    @davidporeilly Do you have the tire loads available in your motec record? We should at least be able to see a more even load distribution with stiffer springs. That would be a surprise if this wouldn't be the case:D.
     
  13. davidporeilly

    davidporeilly Registered

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    I do have the tyre loads. I reviewed them but didn't take a photo. I can do next time I'm on the gaming PC.
    You will be surprised, as in general terms the front right was loaded more with the stiffer setup.
    I might need to create a reporting chart for it as I just looked at it manually in the data columns.
     
  14. davidporeilly

    davidporeilly Registered

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    OK @Ozzy
    Here goes. First the graphs. I took the lap with the closest lap times , lap 4 (-0.035 sec) as the overlay will make more sense.
    The data is "Tyre Loads"
    The coloured lines are the softer spring setup.
    1) Full lap-very hard to read.
    10 lap run tyre loads Lap 4.png
    2) Turn 2
    10 lap run tyre loads Turn 2.png
    3) Turn 3

    10 lap run tyre loads Turn 3.png
    4) Exit T2
    10 lap run tyre loads exit T2.png
    What does it all mean?
    Well it's the first time I have ever looked closely at this metric so I can only think as I go here.

    What I think I can see here.
    1) As a general trend there is no discernible difference between the load inside vs outside. (maybe centrifugal force will always win?) IE neither set shows a lesser or greater variance (deduced by comparing the gaps between the lines). Well maybe while running along the straight, but so what?
    2) Most visible if you look at the area just before and just after the vertical blue line in the final slide is the big spikes in wheel loads in the stiffer set. Whereas the softer set maintains a more consistent tyre load. My interpretation is that this means the wheel is oscillating (bouncing) more. It is consistent with the higher temps and higher wear to FR and it's how it felt in the car.

    So where does this leave us?
    I think back to basics and basically suspension exists to keep the wheels in contact with the road. There is a point where stiffness will reduce that functionality. It can be handy when you want to alter fore-aft grip balance to make stiffer the end you want to have less grip.
    However, race teams have been able to spring cars softer ever since the advent of packers and later the advent of 3rd spring. Prior to that they had to spring them stiff to keep them off the track surface.
    Yes there is an inter-connectivity of everything, other stuff can come into play. If setup was simple it wouldn't have taken me 74 pages to try to explain it. The art is to control the chassis movement and maximise grip and balance. But from where I sit it's erroneous to make global statements that "the stiffer the better" and that's what this whole discourse is about.

    We can start to introduce other changes like camber, ARBs, even tyre pressures. No matter what gets tested certain people will not accept it, even casting aspertions on the testers abilty to get the best out of a setup on a 26 sec oval!
    I however am convinced enough and won't be doing any more.

    Thanks for your interest.
     
    Last edited: Jul 4, 2018
  15. Ozzy

    Ozzy Registered

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    @davidporeilly Thank you very much for your effort!
    As you mentioned it is not easy to see, but I think there is a small trend, that the black lines are closer together than the colored ones. But maybe I just want to see it. Could you create a function, which plots the distince between the tire loads? Something like |FL-FR|, |RL-RR|, |(FL+RL)-(FR+RR)|. That would be super nice. ;)
    Ohh and maybe the average distance over a whole lap or corner.:D
     
  16. davidporeilly

    davidporeilly Registered

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    No. ;)
     
  17. Korva7

    Korva7 Registered

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    So davidporeilly is saying that suspension can be too stiff and andregee is saying that suspension can be too soft.
     
  18. Andregee

    Andregee Registered

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    Depending of the track surface all might be. I know what i will do, if i get a hotter front right tyre on a flat track, i will choose stiffer rear springs and or a stiffer rear anti roll bar. Only if i get problems with the bumps, i will choose a softer front setting, because as I already mentioned, simply choosing harder springs all around without keeping the balance of the vehicle does not prove that there will be less grip in the end.
    If one axle is loaded more than the other while cornering, it is not a question of the basic spring hardness, but of the proportion which the axle contributes to supporting the vehicle against the lateral inclination and if one axle contributes too much to this, which manifests itself in excessively wearing tyres on this axle, then one has to integrate the other axle more strongly by stiffening it, in addition to bumps cause unrest in the vehicle, then one selects a softer set-up in front, then the vehicle also supports itself more strongly on the other axle.
     
  19. davidporeilly

    davidporeilly Registered

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    Except that it doesn't work like that. Stiffening one axle doesn't integrate it more in supporting the car it pushes the weight away towards where you have softer springs.
    The springs don't just push the tyre into the road, the weight of the car does that, springs manage where and for how long the chassis hangs/oscillates. A stiffer spring lowers grip at that end by causing the chassis to hang for longer at the other end.
    Yes a stiffer rear will reduce front right overheating, but it does so by sliding more and rotating more at the rear by reducing grip not by doing more work.
     
  20. Andregee

    Andregee Registered

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    You don´t understand the basics,
    It is not a question of distributing the load forward with harder springs at the rear. Harder springs offer more resistance to lateral inclination/body roll when cornering and if the springs are much harder at the rear than at the front, then they offer much more resistance to lateral inclination/body roll, which means that the wheel load difference at the rear axle is greater than at the front, which means that the outer wheel loses more grip at the rear axle than the inner wheel gets more so that overall more grip is lost than at the front axle.Thats the way how you can play with over- or understeer.
    Choose stiffer springs and relieve the other axle from having to brace against the lateral inclination/body roll and get more grip on the unloaded axle. Thats the same way how to play with anti roll bars to adjust the under and oversteer behaviour.

    The speed of the compression and rebound processes is mainly controlled by the dampers. Harder springs therefore naturally require an adjustment of the dampers to control the spring in and out, so it is clear that a simple choice of harder springs is not appropriate.

    No, its all about the question of wheel load difference.
    Stiffen one axle and you lose grip compared to the other axle, that is undisputed and exactly the proof that the wheel load difference is the decisive factor. If both axles are stiffened in such a way that the vehicle tends to have less lateral inclination despite neutral driving behaviour and thus reduces the wheel load difference on both axles, then the overall grip is increased if the wheels remain in contact with the track on a flat surface
    Not when its done correctly with the correct setup values.
     
    Last edited: Jul 5, 2018

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