Official alignment values thread

Discussion in 'GT4 Tuning' started by Greyout, Feb 28, 2005.

  1. Scaff

    Scaff Staff Emeritus

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    Good summary, but I would raise issue with toe having little effect in anything but higher speed corners, the effect on initial turn-in and oversteer (particularly in FWD) can be felt in slower cornerss as well.

    The Japanese version of GT4 does state which direction is Toe in and out, and that shows negative figures as Toe-in and positive as Toe-out, the Official guide also says the same.

    While Suchayo's images are very interesting, I have an issue with pictures of just extreme values shown, I have previiously asked for pictures showing the gradual change on toe values (say in 10 point increases) but these have never materialised.

    Regards

    Scaff
     
  2. sucahyo

    sucahyo

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    I doubt it would be usefull since I already post some image with toe value of 10/20, 30/40, 50/60, 70/80, 90/100, 110/120.
     
  3. Scaff

    Scaff Staff Emeritus

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    My apologies, I must have missed that one.

    I still find it very strange that the posted pictures are totally at odds with what PD indicate on the Japanese version of the game and what is stated in the Official guide (not that the official guide is that accurate in places).

    Ta

    Scaff
     
  4. sucahyo

    sucahyo

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    Yes, I wish I can read japanese so I can find out what the PD programmer has said about this (if any).
     
  5. 94_XJ

    94_XJ

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    As a computer programmer, this makes no sense to me...but could it be possible that the inversions between Japanese cars and US cars (for example) could be carried over into the game? I believe Grayout stated that with a GTO, a positive number increased oversteer; however, on an S2000 a negative number had the same effect.

    I for one spend hours tuning the suspensions on GT4 so the cars feel just right to me. Even so, I have always been confused as to which way was which.

    I'll experiment tomorrow with different cars from different manufacturers and places of origin to find out for myself. If nothing else, at least I can form my own opinion! :)
     
  6. 4DSC

    4DSC

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    How can positive camber cause oversteer in ANY car?
     
  7. Scaff

    Scaff Staff Emeritus

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    The entire discussion over the last six or so pages is in regard to toe not camber.

    However if a car was set to produce positive rear camber it could certainly result in oversteer if the front end maintaind grip.

    It would not be well controlled, but its possiable.

    Regards

    Scaff
     
  8. 4DSC

    4DSC

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    I don't think I follow. The general idea is that negative camber will give oversteer. Which is why it's the only adjustment you can make in GT4 on camber.
     
  9. Scaff

    Scaff Staff Emeritus

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    No the general idea of negative camber (or camber as a subject in its own right) is not that it will give you under or oversteer (it can be used to trim these characteristics however), rather that its used to control the position of the tyres contact patch relativeto the road surface during cornering. Exactly how it will effect this relationship will depend on a wide range of factors, including tyre size (particularly sidewall ratio ), roll-angle, suspension type and geometry, etc.

    The following is taken from my GT tuning guide (link in my sig) on Camber tuning, most of which relates to real-world camber set-up (admitidly on a much more basic level) and should help explain.

    Camber Settings
    Camber is the angle of the wheel relative to vertical, as viewed from the front or the rear of the car. If the wheel leans in towards the chassis, it has negative camber; if it leans away from the car, it has positive camber.

    GT4 only uses negative camber, as positive camber is very rarely used on cars set up for racing or track work, its function being limited to the set-up of production road cars.

    The principal purpose of setting camber is to ensure that the maximum area of the tyres contact patch is used during cornering. As a car corners the suspension and movement of the tyre cause the contact patch to change size as the car rolls.

    The downside is that with negative camber the contact patch is minimised when the car is not turning which can reduce straight-line traction for the driven wheels and stability. Also setting too extreme a camber value may mean that the full contact patch of the tyre is never used even during hard cornering.

    As camber settings will affect the level of grip at the front and back of the car, it can be used to trim under and over steer if required. Personally I would rarely do this as my main aim with camber is simply to maximise traction while cornering. The rest of the suspension settings can be used to help control under and over steer characteristics. This is however a personal choice based upon the tuners driving style and sometimes the demands of a particular car.

    Setting camber is something of a black art as it is only possible to estimate the effect and only through testing will the correct setting be discovered.


    Overall Camber Settings
    Front Camber
    Advantages
    • Increases cornering grip for the front tyres up to a point after which grip will reduce.
    • Reduces understeer.

    Disadvantages
    • Reduces straight-line traction (for FWD/4WD cars) and stability.
    • Braking distance increases and stability reduced.
    • Very high settings can reduce initial turn-in.


    Rear Camber
    Advantages
    • Increases cornering grip for the rear tyres up to a point, after which grip will reduce.
    • Reduces Oversteer.


    Disadvantages
    • Reduces straight line traction (for RWD/MR/4WD/RR cars) and stability.
    • High settings can increase oversteer as the contact patch is distorted.
    • Less warning when the limited is reached.


    The above has been tested over hundereds of hours and a huge range of cars in GT4 and is an accurate reflection of the effects of camber changes. It is however, as I mentioned above, a gross simplification of how camber works in the real world.

    The following is taken from ART's website and gives a (slightly) more in-depth look at camber.

    WHAT IS CAMBER?

    Camber is the angle of the wheel relative to vertical, as viewed from the front or the rear of the car. If the wheel leans in towards the chassis, it has negative camber; if it leans away from the car, it has positive camber (see next page). The cornering force that a tire can develop is highly dependent on its angle relative to the road surface, and so wheel camber has a major effect on the road holding of a car. It's interesting to note that a tire develops its maximum cornering force at a small negative camber angle, typically around neg. 1/2 degree. This fact is due to the contribution of camber thrust, which is an additional lateral force generated by elastic deformation as the tread rubber pulls through the tire/road interface (the contact patch).

    To optimize a tire's performance in a corner, it's the job of the suspension designer to assume that the tire is always operating at a slightly negative camber angle. This can be a very difficult task, since, as the chassis rolls in a corner, the suspension must deflect vertically some distance. Since the wheel is connected to the chassis by several links which must rotate to allow for the wheel deflection, the wheel can be subject to large camber changes as the suspension moves up and down. For this reason, the more the wheel must deflect from its static position, the more difficult it is to maintain an ideal camber angle. Thus, the relatively large wheel travel and soft roll stiffness needed to provide a smooth ride in passenger cars presents a difficult design challenge, while the small wheel travel and high roll stiffness inherent in racing cars reduces the engineer's headaches.

    It's important to draw the distinction between camber relative to the road, and camber relative to the chassis. To maintain the ideal camber relative to the road, the suspension must be designed so that wheel camber relative to the chassis becomes increasingly negative as the suspension deflects upward. The illustration on the bottom of page 46 shows why this is so. If the suspension were designed so as to maintain no camber change relative to the chassis, then body roll would induce positive camber of the wheel relative to the road. Thus, to negate the effect of body roll, the suspension must be designed so that it pulls in the top of the wheel (i.e., gains negative camber) as it is deflected upwards.

    While maintaining the ideal camber angle throughout the suspension travel assures that the tire is operating at peak efficiency, designers often configure the front suspensions of passenger cars so that the wheels gain positive camber as they are deflected upward. The purpose of such a design is to reduce the cornering power of the front end relative to the rear end, so that the car will understeer in steadily greater amounts up to the limit of adhesion. Understeer is inherently a much safer and more stable condition than oversteer, and thus is preferable for cars intended for the public.

    Since most independent suspensions are designed so that the camber varies as the wheel moves up and down relative to the chassis, the camber angle that we set when we align the car is not typically what is seen when the car is in a corner. Nevertheless, it's really the only reference we have to make camber adjustments. For competition, it's necessary to set the camber under the static condition, test the car, then alter the static setting in the direction that is indicated by the test results.

    The best way to determine the proper camber for competition is to measure the temperature profile across the tire tread immediately after completing some hot laps. In general, it's desirable to have the inboard edge of the tire slightly hotter than the outboard edge. However, it's far more important to ensure that the tire is up to its proper operating temperature than it is to have an "ideal" temperature profile. Thus, it may be advantageous to run extra negative camber to work the tires up to temperature.

    [​IMG]

    (TOP LEFT) Positive camber: The bottoms of the wheels are closer together than the tops. (TOP RIGHT) Negative camber: The tops of the wheels are closer together than the bottoms. (CENTER) When a suspension does not gain camber during deflection, this causes a severe positive camber condition when the car leans during cornering. This can cause funky handling. (BOTTOM) Fight the funk: A suspension that gains camber during deflection will compensate for body roll. Tuning dynamic camber angles is one of the black arts of suspension tuning.


    The full article (covering Caster (not found in GT4) and toe) can be found here

    http://www.advancedracing.com/chassissetup.php

    And should you wish I can recomend further, far more in-depth, information sources.

    Regards

    Scaff
     
  10. GTfreek07

    GTfreek07

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    i generallly have the same set up for all my cars (with a few exceptions) but i have the driving aids on, does changing camber make any difference to the cornering, or only with the aids off? any advice would be helpful :dopey: :D :tup:
     
  11. Scaff

    Scaff Staff Emeritus

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    Being totaly honest the driving aids, particularly if still set at the default values, will remove almost every set-up effect (except the very extreme).

    Camber can and does have a huge effect on the cornering ability of a car, and can also effect it acceleration and braking performance, depending on how it is set and the car in question.

    I would recomend two things, the first is to download my GT4 tuning guides, which can be found in a stickied thread at the top of this sub-forum (or by clicking on the link in my sig), print the first one off and have a good read.

    The second thing would then be to turn off the driving aids and follow the example of a tune from the first guide.

    After that feel free to ask any questions you have.

    Good luck and regards

    Scaff
     
  12. 4DSC

    4DSC

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    Thanks alot for that info.. Lots of interesting stuff. I guess from what I understood in the article, in real life, negative camber doesn't always mean oversteer. But in GT4, apparently it does.
     
  13. sucahyo

    sucahyo

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    No, it is the same. Using 12.0 camber at front will make your car understeer.
     
  14. 4DSC

    4DSC

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    You mean oversteer? Why would it understeer?
     
  15. Scaff

    Scaff Staff Emeritus

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    I would agree that setting camber as high as 12 at the front of any car will almost certainly result in very little grip.

    However to then simply state that this 'will make your car understeer' is a step too far, it depends entirely on how the rest of the car is set-up. what part of a corner you are in, the weight balance of the car at that time, etc.

    Blanket statement about a car always doing X, Y or Z from a single suspension setting are rarely ever correct.

    Regards

    Scaff
     
  16. sucahyo

    sucahyo

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    If you increase camber, lateral grip of the tire will improve only until certain point, where it will decrease. The grip will be reduced if the tire surface not perfectly flat with road surface anymore when cornering. Camber is used to get perfectly flat contact with road when doing cornering.

    Scaff is right about understeer. Even if you set front camber to 12.0, if you set rear rear camber to 25.5 or something, the car will be oversteer. In my experience though, 12.0 front is more understeer than 0.0 camber.

    Make the car sideways (both front and rear slipping at the same amount) and experiment with camber to see how camber affect grip.
     
  17. 4DSC

    4DSC

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    I think I see what you guys are talking about. Kinda started looking at this in a different way. I always thought the reason the car is easier to turn when you increase camber, is because the wheels are being positioned a certain way for where turning becomes easier. Now after sucahyo's post, Im getting a better idea of it. Camber is like a way of having the wheels at a position as if they are already in a turn, when the car infact isn't. Now once the car does enter a turn, the tire/suspension is already waiting in that perfect turning position. :)
     
  18. Rotary Junkie

    Rotary Junkie Premium

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    The way I've always seen camber: It adds tilt to the wheel/tire combo so that during a turn the absolute maximum amount of contact patch is available for comment. Also, softly sprung cars don't need as much camber, because as the suspension compresses, camber is added. And when it expands? Takes camber away.

    Ever wonder why FoMoCo trucks with the twin I-Beam suspension eat the inside edge of the front tires? Well, the springs get worn out, and more importantly, SOFTER, so the nose compresses, adding negative camber.
     
  19. Scaff

    Scaff Staff Emeritus

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    I've only just noticed this one (must spend more time here) and I must correct this slightly. While the relative stiffness of a spring will effect the degree of camber gained (softer springs allow more travel for the same level of force), they do not determine if that camber gain is positive or negative at all. That would be determined by the suspension geometry itself.

    You are right that this can lead to an increase in inner tyre wear, however its far from the only cause. In-correct tracking (often caused by hitting the curb or a large pot-hole) can also cause the same problems, as can wear to the suspension bushings (which can alter the geometry). However its generally a combination of the factors that causes problems rather than one single cause.

    Regards

    Scaff
     
  20. jinxtigr

    jinxtigr

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    Just a note about the great confusion on toe angles from a programmer guy...

    To know what affects the car's functional handling in GT4, you have to drive it and see whether the toe setting increases understeer or oversteer. That's the 'bible' for toe settings. It's going to be the same for all cars, so find one that's very sensitive and makes it obvious. Sounds like negative is toe-in and positive is toe-out, functionally, in GT4.

    IGNORE the rendering of the tire in GT4 and pay attention only to handling. Why? Because the rendering of the tire is a separate routine from the physics model and none of us can possibly confirm whether the toe angles are depicted properly- or reversed from the physics model. It's normally a very small adjustment so it's just the sort of bug that could get by you unnoticed. The rendering of the tire DOES NOT STEER THE CAR. It's only a picture of the car as it drives. The entire car could be depicted driving sideways without the physics model being any different. Basically you're hoping the rendering of the car exactly depicts the finest details of what the physics model of the car is doing. Probably is, but you can't be absolutely sure about the smaller details.

    Again, I may not be a car tuner (though I am understanding what's said, and I love that stuff) but I'm a coder, and it needed to be said. You have to go by the behavior of the modeled vehicle, not the rendering, as the authoritative answer. It would be a very simple programming error to have the toe working oppositely from how it's depicted. Literally one symbol in error, a plus for a minus or a minus for a plus. The normal steering of the wheels and the rendering of that needn't be affected, either. Toe is a tiny additional factor that normally won't be visibly important...
     
  21. sucahyo

    sucahyo

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    It's not that simple. If you change the rear toe only to negative or positive, both setting can make the car oversteer. We can't make conclution just from understeer or oversteer behaviour.

    If you ever drive Grand Prix Legend, you will learn that:
    - positive rear toe in increase car stability at straight, and IMO car tend to sideways more .
    - negative rear toe in decrease car stability at straight, make it wandering around, and IMO car tend to spin out more.

    You need to mention how you got this conclution.

    We can use a big number for toe using hybrid. IIRC -6.xx to +6.xx in GT2, and -128 to +127 in GT4. This kind of value will make both visual and handling differences very noticable.

    Can you give example or maybe a flowchart of what you think about GT4 physics engine algorithm? Even if it is separated routine, I doubt PD is that careless. The visual should display according to simulation engine status. For example:

    player input: Now the front wheel steering is at 10 degree to the right.
    main routine: current car roll angle is at 1 degree, direction at this (x,y,z), with speed at this (x,y,z), with rotation at this (x,y,z), with front toe set to 0.1 degree and caster at 1 degree that make the wheel final toe for right front wheel at 10.1 degree and wheel camber at 2.1 degree (just an example). do this to other tire too.
    main routine: inform this to visual routine and physics handling routine.
    physics handling routine: current right front tire load is at xxxx, use soft tire data to calculate, the next right front tire grip should be at xxxx, calculate other tire too.
    visual routine: calculate model position and angle in 3D coordinate, render using camera number xx


    The above is just an illustration of what I think GT4 flow is. There should be a LOT of things that I miss.

    What I am trying to say is: if the toe setting render routine is wrong, then what we see when the car turn would be wrong too (backward). I don't think that's the case. I think the toe setting will be added before both physics handling routing and visual routine. So both should receive the same number.

    I don't think that's the case, PD do render it, as can be seen when we hack the toe of both GT2 and GT4.

    [​IMG][​IMG]

    [​IMG][​IMG]

    The visual and handling do not go to different way, both is synchronized.