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Optimum tyre camber

Discussion in 'Assetto Corsa' started by Giovaneveterano, Oct 12, 2017.

  1. Giovaneveterano

    Giovaneveterano
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    Every time I pick a new car the first thing I change into the setup are the tyres as the whole lap time comes from them.
    Camber is a key value around the optimum tyre performance, it influences the temperature and the grip both longitudinal and lateral.

    Besides the "inner-out temp delta", how can I measure the tyre grip as the camber change? How can I find the right spot on a given tyre?
    Probably it's dark magic, but I'm sure that some powerful wizard is somewhere here :p
     
  2. Kek700

    Kek700
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    Something I would like to know too
     
  3. RasmusP

    RasmusP
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    Me too!
    After reading and trying a lot about setups I decided to take it slowly and learn about one thing after another in detail and learn how it really feels.
    I do know now:
    Aero, ARBs, pressure, compound, fuel, ride height + rake, brakes, toe.
    I am learning at the moment but already doing okay:
    Springs, dampers, fast dampers.

    But camber... I had some great talk with @BhZ about it and it seems like you need to test it! And it's one thing that is different for every sim!

    My thoughts: you start cornering, the weight shifts, the chassis bends and the suspension starts to work.
    Now without camber the tyre patch with the biggest load would be with positive camber because of it, so you need to counter this with negative camber.

    Yeah, we all know that...
    But then the tyre flexes, slips and bounces and it's impossible to get it perfect. Even if you get it perfectly for one turn, it can be completely wrong for another turn!

    So in the end you have a "range" for the perfect camber setting and I think the default setups are pretty much on spot!
    The only way to optimise it further is to test what's faster. And to try to feel what feels better!

    Last week I tried to do this with the Tatuus at Silverstone International and the sweeping right-hander after the hangar straight was a good corner to test it.
    With too low (+ value) camber you had more grip at turn in and exit. You could feel that there was simply more rubber in contact with the tarmac.
    But mid corner the car got a bit floaty and I couldn't feel the limit as good anymore.

    With higher camber (more minus) the turn in and the exit felt bit more agile but less precise. Mid corner it felt better. I didn't have exactly more grip but the "getting dragged to the outside" felt more controllable. It wasn't on/off anymore but more like a controlled drift (on all 4 wheels).

    Then I tested it for front and rear separately and the same feeling happened to each axle individually. I ended up with a bit less camber at the front and slightly more camber at the rear.
    That way the front had the maximum grip and the rear came around better (I had some little understeer in that turn) while being more controllable at the same time!

    Then of course you have temperatures and wear etc etc.
    I'd say for short distances go for more camber, for longer stints go for less camber!
    My new rule by thumb is:
    More camber: less grip but better feel, faster turn in, more wear
    Less camber: more grip but snappier. Slower turning and less wear

    Of course that only applies for reasonable settings! If you go out of range you will definitely end up with way less grip and strange behavior!

    And importantly: when you go for softer suspension or anti roll bars you will need more camber as the chassis will bend more. The stiffer everything is, less camber is needed.

    Also don't forget that ride height changes will alter the camber and toe setting! So load up the default setup for a car and write down the toe and camber values from the live screen!
    For the Tatuus I mostly soften the springs a little bit and put the ride height down. The camber increases by "3-4 clicks" minus! So after doing this I definitely won't go any higher with the camber and only use the "+"-button :)
     
    Last edited: Oct 13, 2017
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  4. Rob Every

    Rob Every

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    In RF you could gauge how your camber was working in some mods by the tyre temps, some of them were very accurate and it really made a difference to how the car worked. SO if you had a relatively even temp spread you knew you could up the camber a bit. Obviously tyre physics in sims has moved on a bit.

    I never make drastic changes to camber, but if it seems excessively low like 0.7 neg, I might raise it to 1.3 or something.

    Some cars have weird ride heights, like the GTR GT3 for instance has massively high front ride height, yet both BMW cars have the car pointing on the nose as default. Both are front engined rwd basically.

    Yes changing it made little difference to feel.

    I don't know enough about shocks and springs, might raise the strength of a spring on a flatish track, or make the bumpstops travel longer at somewhere bumpy like Brands or Zandvoort.

    But by far the most important thing to do at those two tracks would be to fit differnet compound tyres left and right side, and you cant do that, which is very annoying!! So I just raise the pressures
     
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  5. BhZ

    BhZ
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    I shall summon @PhilS13 hoping that he can help :)
     
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  6. RasmusP

    RasmusP
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    I'll help you!
    @PhilS13 :devilish::devilish::sneaky:

    PS: I obviously have no clue about the "real" thing either but I wrote down my current state of thoughts and knowledge, maybe it helps but please feel free to rip it all apart! We are here to learn, not to be right :)
     
  7. SirVanhan

    SirVanhan
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    Until a few builds ago, you could put maximum camber with no side effects. However, I don't know if it was ever fixed.
     
  8. Kek700

    Kek700
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    The problem i have is keeping an eye on tyre temperature readings whilst driving.
    This is made twice as difficult because my replay does not seem to record tyre information.

    I drive so inconsistantly that with out a replay of tyre temps it is difficult to arrive at a conclusion.
    This means it becomes a laborious slog of circulating around and around the track to observe
    one corner, unfortunately having the memory of a goldfish does not help.:rolleyes:
    I would not say i am bad at setting a car up, just limited in gathering sufficient tyre information.
    I have thought about data logging, but it is a complexity i do not really want.
    I usually dive a Nissan gt3 gtr, admittedly not very well, it has taken me a lot of fiddling
    to get this car working well for me, mostly by guess work and time spent in the car.
    It sort of puts me off driving anything else, ( Tatuus for example ) it is one reason for
    my driving our fixed setup series, no one but "me" to blame.
    I see this as most important, because after all the technical details have been explored
    It all comes down to the tyres were the performance of your driving exists.
    Now if i could borrow BhZ's brain, that would be a big improvement in my driving
    and i would not give a :poop: about tyres.:)
     
  9. PhilS13

    PhilS13
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    Forget temperatures and wear, the effect of camber on those is too small.

    The more camber you run the more longitudinal grip you lose. However the loss is rarely enough to say : "I'm gonna sacrifice lateral grip to keep some longitudinal."

    So looking at lateral grip alone, each tyre has a camber at which it will deliver the most lateral force. On GT3 cars for example it's -3.6°. Formulas are on the Kunos forum. That doesn't mean you have to set it to -3.6° in the pits.

    While cornering the body rolls, the suspension moves and each tyre will fall to a different "mid-corner" camber. If at that precise moment, for example the outside front moves to -3.6° mid-corner, then you know that this tyre alone is giving the most lateral grip it can at that moment. That doesn't mean you should setup for -3.6° mid-corner.

    The inside tyre is contributing as well and if you really want to find the peak lateral grip you need to take it into account. It will be more or less unloaded depending on the car and will usully sit at an akward -4.x° mid-corner, but in the direction opposite to the force you are asking the tyre to give. How much it is actually contributing and how much you should sacrifice on the outside to "help" the inside involves math and if you understand what I just said you'll likely manage to figure out the math.

    If not, do it by feel. It works just as good. Just do one end at the time and try to spot the balance change.
     
    Last edited: Oct 13, 2017
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  10. RasmusP

    RasmusP
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    Awesome post! :confused:

    So to get "the math" I would probably need "the formulas" first?

    But what you said: -3.6° mid corner is the optimum for the loaded tire. Then you have a "balance of grip" from the outside, loaded tire and the unloaded, inside tire.
    For example 80/20. So my fantasy math would be something like:
    Grip = 0.8*(-3.6°) + 0.2*(-4.2°)
    -3.6° = 1 (100%)
    -4.2° = 0.6 (60%) -> yes, here begins the need for the formula!

    And the question then is if -3.6 and -4.2 result in the most grip or if -3.4 and -4.0 are better in the end.

    Of if you go asymmetrical because the math is different for different corners. Silverstone Int. I could imagine would be a good example. All righthanders are heavily loaded turns while there is only one really loaded lefthander...

    You probably do a facepalm now because I have no clue about the math and formula (will search for it later!) but I wanted to write down what my stomach/thumb need to try to aim for :)

    EDIT: I just tried to find anything @PhilS13 , looked at all your threads over there too. I found that you can read something out of the tyres.ini in the sdk folder but I could use some help to turn my head in the right direction for further research :)
     
    Last edited: Oct 13, 2017
  11. LeSunTzu

    LeSunTzu
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    I don't think they did.
    Unlike in a game like rF2, the camber has little effect on wear and temps in AC.
     
  12. Mr Deap

    Mr Deap

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    Guess other sims are all the same then...
     
  13. PhilS13

    PhilS13
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    Search for DCAMBER_0 and at some point you'll find the formula. Searching for terms like LS_EXPY will give load sensitivity info and you'll be able to determine tyre contribution. Keep in mind the calc will be assuming both tyres operating at peak slip angle...on some cars the suspension geometry will not allow that.

    There is even an app(camber extravaganza) that attempted doing the math for it. I don't know if the result ended up ok but he was on the good path early on iirc. The code of the app will likely show you.

    At tracks like Silverstone Int and Donington national asymmetric is way faster but other than that it's rare to see gains out of asymmetric setups. You don't need a lot of corners "the wrong way" for the asymmetric gains to vanish.
     
    Last edited: Oct 13, 2017
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  14. Kek700

    Kek700
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    The problem I have is that there is no perfect camber setting, especially if there is a lot of
    diversity corner to corner, this was not a problem with active suspension but we have
    springs and dampers.
    My point being that it is difficult to judge a perfect camber setting on the most advantageous
    corner then dial in a compromise for the other corner, this can be done by looking at
    the temperatures across the tyre during a corner, this takes into account ARB , dampers , car ride
    height, these may have been chosen for the whole circuit. ( I just need a temperature reading by
    reading across the tyre per corner.), yes I know about slip angles, this I am again constantly trying
    not to compromise whilst driving. Probably not very successfully.
    I quite often use Toe to fine tune the car, this is noticeable during entry and mid corner bite,
    You can select what you require, more turn in bite at the expense of mid corner grip,
    or go for the reverse.
    There are many small tricks like this to fine tune, but the most important is mid corner ultimate
    grip, including traction, this is were all the lap time is.
    The next big problem I have is that does each setting have a programmed consequence,
    am I adjusting something that is not taken into account, on top of all the other variables.
    A good example of this is aerodynamic rake, I am constantly juggling this, maybe for
    no good reason, it should be an important factor, but is it taken into account!

    I just love a good "rant" :sleep:
     
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