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car.ini > Tires

Discussion in 'Racer Physics and Technical' started by eschefo, Apr 7, 2011.

  1. I'm trying to do an application to change de tires in the car.ini, doing a database of models and sizes (for example, Pirelli Pzero 225/45 R17 94W....... supposed).
    Each model and size with their radius, Pacejka coefficients, relaxation lengths..... The problem is Pacejka!!.

    I have some information:
    1. Cosmo (thanks), coefficients for 195/60 R15 and 225/45 R17
    2. www.tiretrack.com real test with grip coefficientes and more

    And some books,
    3. FUNDAMENTALS of VEHICLE DYNAMICS-Thomas DGillespie-SAE (Chapter 10)
    4. The AUTOMOTIVE CHASSIS Vol 1 Components design-Genta & Morello-Springer 2009 (Chapter 2) with many real curves.
    5. AUTOMOTIVE ENGINEERING-David A Crolla-Elesevier 2009 (Chapter 10.1 and 11.1)
    6. www.members.xoom.alice.it/adiaforo The Pacejka equation-Paolo Pinto
    7. Altering Pacejka coefficients-Olsen & Page, using RACER
    8. Car.ini of differents vehicles...

    but I have many doubts


    Somebody have more information?
    Please, help.:pray:
     
  2. I think I have pacejka data for several tires sizes, if I can find it I'll post it tomorrow night.
     
  3. Ah, tire modelling... :)

    There isn't many publicly available sets of data to feed into pacejka, and the ones that do exist, are sometimes limited (don't behave well other than in regular road-going conditions, or limited racing conditions, etc).

    Tire manufacturers and racing teams do not usually publish such data when they research it, so it's hard to find unless you're already in the industry or pay for the data or for tire tests.

    Most of the existing known data is probably already integrated in existing vehicles for Racer or other sims, so I guess that is the shortest route to get that kind of pacejka-tire-coefficients-database going.
     
  4. Here you go with pacejka data for various size tires and some other info. It was retrieved from RSC, the data was originally done by FSR.
     

    Attached Files:

  5. What tyres are you after eschefo?

    Dave
     
  6. Thx Boomer, that's an old doc & it might be updated...

    About tyres, does anyone knows how the tir files should look like ?
    When compiling to ASCII files, I got a file structure that resembles Shift hdt tyre files....Does anyone tried to plug those values inside pacejka tree ? I could provide here some more Lat=Fy/Long=Fx values from AWD/RWD to drift tyres profiles from Shift...

    It looks something like this in Shift :

    Code:
    [SLIPCURVE]
    Name="Lat"
    Step=0.009000            // Slip step
    DropoffFunction=0.50      // see above            
    Data:
    0.000 0.0042 0.0084 0.0126 0.0168 0.021 0.0252 0.0294 0.0336 0.0378
    0.042 0.0462 0.0504 0.0546 0.0588 0.063 0.0672 0.0714 0.0756 0.0798
    0.084 0.0882 0.0924 0.0966 0.1008 0.105 0.1092 0.1134 0.1176 0.1218
    0.126 0.1302 0.1344 0.1386 0.1428 0.147 0.1512 0.1554 0.1596 0.1638
    0.168 0.1722 0.1764 0.1806 0.1848 0.189 0.1932 0.1974 0.2016 0.2058
    0.210 0.2142 0.2184 0.2226 0.2268 0.231 0.2352 0.2394 0.2436 0.2478
    0.252 0.2562 0.2604 0.2646 0.2688 0.273 0.2772 0.2814 0.2856 0.2898
    0.294 0.2982 0.3024 0.3066 0.3108 0.315 0.3192 0.3234 0.3276 0.3318
    0.336 0.3402 0.3444 0.3486 0.3528 0.357 0.3612 0.3654 0.3696 0.3738
    0.378 0.3822 0.3864 0.3906 0.3948 0.399 0.4032 0.4074 0.4116 0.4158
    0.420 0.4242 0.4284 0.4326 0.4368 0.441 0.4452 0.4494 0.4536 0.4578
    0.462 0.4662 0.4704 0.4746 0.4788 0.483 0.4872 0.4914 0.4956 0.4998
    0.504 0.5082 0.5124 0.5166 0.5208 0.525 0.5292 0.5334 0.5376 0.5418
    0.546 0.5502 0.5544 0.5586 0.5628 0.567 0.5712 0.5754 0.5796 0.5838
    0.588 0.5922 0.5964 0.6006 0.6048 0.609 0.6132 0.6174 0.6216 0.6258
    0.630 0.6342 0.6384 0.6426 0.6468 0.651 0.6552 0.6594 0.6636 0.6678
    0.672 0.6762 0.6804 0.6846 0.6888 0.693 0.6972 0.7014 0.7056 0.7098
    0.714 0.7182 0.7224 0.7266 0.7308 0.735 0.7392 0.7434 0.7476 0.7518
    0.756 0.7602 0.7644 0.7686 0.7728 0.777 0.7812 0.7854 0.7896 0.7938
    0.798 0.8022 0.8064 0.8106 0.8148 0.819 0.8232 0.8274 0.8316 0.8358
    0.840 0.8442 0.8484 0.8526 0.8568 0.861 0.8652 0.8694 0.8736 0.8778
    0.882 0.8862 0.8904 0.8946 0.8988 0.903 0.9072 0.9114 0.9156 0.9198
    0.924 0.9282 0.9324 0.9366 0.9408 0.945 0.9492 0.9534 0.9576 0.9618
    0.966 0.9682 0.9714 0.9756 0.9790 0.982 0.9825
    
    [SLIPCURVE]
    Name="Long"
    Step=0.009000            // Slip step
    DropoffFunction=0.50      // see above            
    Data:
    0.000 0.0042 0.0084 0.0126 0.0168 0.021 0.0252 0.0294 0.0336 0.0378
    0.042 0.0462 0.0504 0.0546 0.0588 0.063 0.0672 0.0714 0.0756 0.0798
    0.084 0.0882 0.0924 0.0966 0.1008 0.105 0.1092 0.1134 0.1176 0.1218
    0.126 0.1302 0.1344 0.1386 0.1428 0.147 0.1512 0.1554 0.1596 0.1638
    0.168 0.1722 0.1764 0.1806 0.1848 0.189 0.1932 0.1974 0.2016 0.2058
    0.210 0.2142 0.2184 0.2226 0.2268 0.231 0.2352 0.2394 0.2436 0.2478
    0.252 0.2562 0.2604 0.2646 0.2688 0.273 0.2772 0.2814 0.2856 0.2898
    0.294 0.2982 0.3024 0.3066 0.3108 0.315 0.3192 0.3234 0.3276 0.3318
    0.336 0.3402 0.3444 0.3486 0.3528 0.357 0.3612 0.3654 0.3696 0.3738
    0.378 0.3822 0.3864 0.3906 0.3948 0.399 0.4032 0.4074 0.4116 0.4158
    0.420 0.4242 0.4284 0.4326 0.4368 0.441 0.4452 0.4494 0.4536 0.4578
    0.462 0.4662 0.4704 0.4746 0.4788 0.483 0.4872 0.4914 0.4956 0.4998
    0.504 0.5082 0.5124 0.5166 0.5208 0.525 0.5292 0.5334 0.5376 0.5418
    0.546 0.5502 0.5544 0.5586 0.5628 0.567 0.5712 0.5754 0.5796 0.5838
    0.588 0.5922 0.5964 0.6006 0.6048 0.609 0.6132 0.6174 0.6216 0.6258
    0.630 0.6342 0.6384 0.6426 0.6468 0.651 0.6552 0.6594 0.6636 0.6678
    0.672 0.6762 0.6804 0.6846 0.6888 0.693 0.6972 0.7014 0.7056 0.7098
    0.714 0.7182 0.7224 0.7266 0.7308 0.735 0.7392 0.7434 0.7476 0.7518
    0.756 0.7602 0.7644 0.7686 0.7728 0.777 0.7812 0.7854 0.7896 0.7938
    0.798 0.8022 0.8064 0.8106 0.8148 0.819 0.8232 0.8274 0.8316 0.8358
    0.840 0.8442 0.8484 0.8526 0.8568 0.861 0.8652 0.8694 0.8736 0.8778
    0.882 0.8862 0.8904 0.8946 0.8988 0.903 0.9072 0.9114 0.9156 0.9198
    0.924 0.9282 0.9324 0.9366 0.9408 0.945 0.9492 0.9534 0.9576 0.9618
    0.966 0.9682 0.9714 0.9756 0.9790 0.982 0.9825
    
    In Racer when compiling from my created pacejka curves :

    Code:
    // ASCII export of Racer's Pacejka Player
    // Values from SR=0.00 to 2.00, 237 steps, Fx normalized
    
    0.00000 0.32983 0.66457 0.82367 0.89082 0.92386 0.94260
    0.95440 0.96240 0.96814 0.97244 0.97577 0.97842 0.98057
    0.98236 0.98386 0.98514 0.98624 0.98720 0.98805 0.98879
    0.98946 0.99005 0.99059 0.99108 0.99152 0.99193 0.99230
    0.99264 0.99296 0.99325 0.99352 0.99378 0.99401 0.99424
    0.99444 0.99464 0.99482 0.99500 0.99516 0.99531 0.99546
    0.99560 0.99573 0.99586 0.99598 0.99609 0.99620 0.99631
    0.99640 0.99650 0.99659 0.99668 0.99676 0.99684 0.99692
    0.99700 0.99707 0.99714 0.99721 0.99727 0.99733 0.99739
    0.99745 0.99751 0.99756 0.99762 0.99767 0.99772 0.99776
    0.99781 0.99786 0.99790 0.99794 0.99798 0.99802 0.99806
    0.99810 0.99814 0.99817 0.99821 0.99824 0.99828 0.99831
    0.99834 0.99837 0.99840 0.99843 0.99846 0.99849 0.99852
    0.99854 0.99857 0.99860 0.99862 0.99865 0.99867 0.99869
    0.99872 0.99874 0.99876 0.99878 0.99880 0.99883 0.99885
    0.99887 0.99889 0.99890 0.99892 0.99894 0.99896 0.99898
    0.99900 0.99901 0.99903 0.99905 0.99906 0.99908 0.99909
    0.99911 0.99912 0.99914 0.99915 0.99917 0.99918 0.99920
    0.99921 0.99922 0.99924 0.99925 0.99926 0.99928 0.99929
    0.99930 0.99931 0.99932 0.99934 0.99935 0.99936 0.99937
    0.99938 0.99939 0.99940 0.99941 0.99942 0.99943 0.99944
    0.99945 0.99946 0.99947 0.99948 0.99949 0.99950 0.99951
    0.99952 0.99953 0.99954 0.99955 0.99956 0.99956 0.99957
    0.99958 0.99959 0.99960 0.99961 0.99961 0.99962 0.99963
    0.99964 0.99964 0.99965 0.99966 0.99967 0.99967 0.99968
    0.99969 0.99969 0.99970 0.99971 0.99971 0.99972 0.99973
    0.99973 0.99974 0.99975 0.99975 0.99976 0.99977 0.99977
    0.99978 0.99978 0.99979 0.99979 0.99980 0.99981 0.99981
    0.99982 0.99982 0.99983 0.99983 0.99984 0.99984 0.99985
    0.99985 0.99986 0.99986 0.99987 0.99987 0.99988 0.99988
    0.99989 0.99989 0.99990 0.99990 0.99991 0.99991 0.99992
    0.99992 0.99993 0.99993 0.99993 0.99994 0.99994 0.99995
    0.99995 0.99996 0.99996 0.99996 0.99997 0.99997 0.99998
    0.99998 0.99998 0.99999 0.99999 1.00000 1.00000 
    
    // Values from SA=0.00 to 2.00 radians, 237 steps, Fy normalized
    
    0.00000 0.15208 0.30770 0.46491 0.61438 0.74347 0.84334
    0.91281 0.95669 0.98187 0.99462 0.99962 1.00000 0.99775
    0.99410 0.98978 0.98523 0.98068 0.97628 0.97209 0.96816
    0.96449 0.96107 0.95789 0.95494 0.95221 0.94967 0.94731
    0.94511 0.94306 0.94115 0.93936 0.93769 0.93612 0.93465
    0.93327 0.93196 0.93074 0.92957 0.92848 0.92744 0.92645
    0.92552 0.92463 0.92378 0.92298 0.92221 0.92148 0.92078
    0.92011 0.91947 0.91886 0.91827 0.91771 0.91717 0.91665
    0.91615 0.91567 0.91520 0.91476 0.91433 0.91391 0.91351
    0.91312 0.91275 0.91239 0.91204 0.91170 0.91137 0.91105
    0.91075 0.91045 0.91016 0.90988 0.90960 0.90934 0.90908
    0.90883 0.90858 0.90835 0.90812 0.90789 0.90767 0.90746
    0.90725 0.90705 0.90685 0.90666 0.90647 0.90629 0.90611
    0.90593 0.90576 0.90559 0.90543 0.90527 0.90511 0.90496
    0.90481 0.90466 0.90452 0.90438 0.90424 0.90411 0.90398
    0.90385 0.90372 0.90360 0.90348 0.90336 0.90324 0.90313
    0.90301 0.90290 0.90279 0.90269 0.90258 0.90248 0.90238
    0.90228 0.90218 0.90209 0.90199 0.90190 0.90181 0.90172
    0.90163 0.90155 0.90146 0.90138 0.90130 0.90122 0.90114
    0.90106 0.90098 0.90090 0.90083 0.90076 0.90068 0.90061
    0.90054 0.90047 0.90041 0.90034 0.90027 0.90021 0.90014
    0.90008 0.90002 0.89995 0.89989 0.89983 0.89977 0.89972
    0.89966 0.89960 0.89955 0.89949 0.89944 0.89938 0.89933
    0.89928 0.89922 0.89917 0.89912 0.89907 0.89902 0.89897
    0.89893 0.89888 0.89883 0.89879 0.89874 0.89870 0.89865
    0.89861 0.89856 0.89852 0.89848 0.89844 0.89839 0.89835
    0.89831 0.89827 0.89823 0.89819 0.89815 0.89812 0.89808
    0.89804 0.89800 0.89797 0.89793 0.89789 0.89786 0.89782
    0.89779 0.89775 0.89772 0.89769 0.89765 0.89762 0.89759
    0.89755 0.89752 0.89749 0.89746 0.89743 0.89740 0.89737
    0.89734 0.89731 0.89728 0.89725 0.89722 0.89719 0.89716
    0.89713 0.89710 0.89708 0.89705 0.89702 0.89700 0.89697
    0.89694 0.89692 0.89689 0.89686 0.89684 0.89681 0.89679
    0.89676 0.89674 0.89672 0.89669 0.89667 0.89664 
    
    Notice I have the same nb. of steps (237) for both profiles...I guess the inverse could be easily done, creating custom tyres for Shift easily :) but that isn't my goal right now.
     
  7. @eschefo

    Pacejka is tremendously powerful & you guys should really debug it with a steering wheel since the aligning force acts on the FFB.

    After some days playing with it, I can now tell how the whole works approximately. Since tyres are connected to the car, the body aero, the differential, the wheels props & the suspension + even the gears ratios have a HUGE impact on the 'output' behavior felt on steering wheels. So, you should set this accordingly or simultaneously when editing the Pacejka curves.

    Basically, the curvatures of the 3 curves determines how the car will slip or grip, @ long & lat direction. The coefficients as you have seen from the code source use some car.ini props/variables like camber & rolling_coeff from your wheels. So that's also quite important to know.

    So, admit you want a drift car, what you would need is :

    - enough engine torque
    - a nicely balanced car => aero for pressing the car to the road
    - a viscous/LSD diff
    - a good CoG pos & physical car props
    - quite stiff suspension & calibrated tyre damping / tire rates
    - both long & lat curve set quitely high in the graph
    - aligning moment is really a question of taste which can be counter-balanced with your profiler & with Racer 'new' wheel settings.

    Also, if you're not satisfied (FFB steering wheels), the 'grip <x>' command in Racer allows you to approximately 'fix quickly' your Pacejka profile, but I wouldn't recommend it.

    ==================
    I was lately thinking about dynamical Pacejka programming in Racer, so it means 'interpolation' of coeff values thru profiles over time or 'triggered events' via scripts, hope Ruud or Mitch will brainstorm a bit...instead of implementing a static grip value over splines => look in Tracked for more infos.
     
  8. [​IMG]

    Code:
    pacejka
    {
      ; Pacejka constants (Pacejka96 model)
      model=0
      ; Lateral coefficients
      a0=1.79900
      a1=38.00000
      a2=1758.00000
      a3=2799.00000
      a4=2.65000
      a5=0.00000
      a6=-0.17000
      a7=1.00000
      a8=0.00000
      a9=0.00000
      a10=0.00000
      a111=0.00000
      a112=0.00000
      a12=0.00000
      a13=0.00000
      ; Longitudinal coefficients
      b0=0.82600
      b1=25.00000
      b2=1839.00000
      b3=0.00000
      b4=229.00000
      b5=0.00000
      b6=0.00000
      b7=0.00000
      b8=-10.00000
      b9=0.00000
      b10=0.00000
      ; Aligning moment coefficients
        c0=2.48
        c1=-3
        c2=-2.7
        c3=-0.5
        c4=-5.2
        c5=0
        c6=0
        c7=0.044
        c8=-0.58
        c9=0.18
      c10=0.00000
      c11=0.00000
      c12=0.00000
      c13=0.00000
      c14=0.00000
      c15=0.00000
      c16=0.00000
      c17=0.00000
      ; Statistical data (SR, SA in radians)
      optimal_slipratio=1.98621
      optimal_slipangle=0.07704
    }
    
    For now, I left the camber, horizontal + vertical shift coeff.

    Try it out, it feels quite amazing on my G25, for sure it depends on many settings...:)
     
  9. Knut Omdal Tveito

    Knut Omdal Tveito
    Premium Member

    I found that numerical simulations were really useful in tire modeling, especially for learning the physics behind it (velocity effects, load-sensitivity, combined slip etc)

    With the finite element method the only input is the tire construction (ply specs, thread design, aspect ratio etc). I found some literature with data on goodyear-compound and with this data the model was really close to experimental data.

    I haven't had time to do any modding for a long time now, but the tires I modeled were feeling quite good, once I corrected the errors I first made:)

    If anyone's interested and I can dig up my results, I would be happy to share them.

    [​IMG]
    [​IMG]
    [​IMG]

    Uploaded with ImageShack.us
     
  10. Alexander Knoll

    Alexander Knoll
    NEVER GIVE UP!!

    oh yes please...this is atm always a secret book for me......
     
  11. Your Lat (Fy) curve looks quite like mine...

    For the Mz curve, it's imo too high, so 'theoretically' you would feel too much force on your steering wheel...

    Here's the rest of Shift hdt tyres code :

    Code:
    [COMPOUND]
    Name="Hi-Performance Street"
    Style=1                                                // 0 = treaded, 1 = slick, 2 = wet
    ALL:                                                   // Arguments:ALL,FRONT,REAR,LEFT,RIGHT,FRONTLEFT, FRONTRIGHT,REARLEFT,REARRIGHT
    DryLatLong=(1.760, 1.760)                              // Lateral/longitudinal coefficients in dry weather
    WetLatLong=(1.720, 1.720)                              // Lateral/longitudinal coefficients in wet weather
    DrySlide=1.68                                           // sliding coefficient in dry weather
    WetSlide=1.56                                           // sliding coefficient in wet weather
    CorneringStiffness=30000.0                               // Base Cornering stiffness (N/rad)
    BrakingStiffness=30000.0                               // Base Braking stiffness (N)
    SelfAligningStiffness=3500                               // Self aligning stiffness (Nm/rad)
    CamberStiffnessRelative=0.1                            // Example: 0.1 setting gives for 1 deg camber nets 0.1 deg toe in
    RadiusRPM=0.00                                         // Increased radius per unit RPM
    SpringBase=60500.0                                      // Base spring rate with no pressure ( 1050lb/in @ 170kpsi)
    SpringkPa=560.00                                         // Spring rate per unit pressure
    Damper=575.0                                           // Damping rate of tire
    SpeedEffects=(2000.5,15.0)                             // Speed at which grip drops to half (m/s, 0.0 to disable), speed load equivalency (see above)
    LoadSens=(-3.10e-6, 0.80, 15000.0)                     // Load sensitivity of tire (initial slope, final grip multiplier, final load)
    LatPeak=(0.20, 0.20, 9500.0)                           // Slip range where lateral peak force occurs depending on load
    LongPeak=(0.20, 0.20, 9500.0)                          // Slip range where longitudinal peak force occurs depending on load
    HeatBasePeak=(0.17,0.5)                                // static peak slip to compute friction heat, fraction of static peak slip to use (the remainder will be the dynamic peakslip)
    LatCurve="Lat"                                         // Slip angle curve (data uses normalized angle)
    BrakingCurve="Long"                                    // Slip ratio curve under braking
    TractiveCurve="Long"                                   // Slip ratio curve under acceleration
    CamberLatLong=(0.50, 0.05, 0.0)                        // Peak camber angle, lateral gain at peak, longitudinal loss at 90 degrees
    RollingResistance=1300.0                               // Resistance torque (Nm) per unit deflection (m) on ground
    Heating=(6.00e-1, 6.00e-3)                             // Heat caused by (rolling, friction)
    Transfer=(12.00e-3, 2.00e-3, 2.00e-4)                  // Heat transfer to (road, static air, moving air)
    HeatDistrib=(12.00,300.0)                              // (Max camber angle, max off-pressure) that affects heat distribution (higher number -> less temperature difference)
    AirTreadRate=0.020                                       // Heat transfer between tread and inside air
    WearRate=0.152e-6                                        // Wear rate constant
    Softness=0.55                                             // Softness is now just for AI strategic use
    AISens=(0.80,25650.0)                                  // Simplified AI load sensitivity (final grip mult, final load)
    AIGripMult=1.20                                        // Grip multiplier for AI vehicles (due to tire model simplification)
    AIPeakSlip=0.105                                       // Simple peak slip angle for AI vehicles
    AIWear=0.413e-7                                        // AI wear rate constant
    Temperatures=(80.0,20.0)                               // Optimum operating temperature for peak forces, cold starting temp (Celsius)
    OptimumPressureBase=100.0                              // Base pressure to remain flat on ground at zero deflection
    OptimumPressureMult=0.0400                             // Multiplier by load to stay flat on ground
    GripTempPress=(0.55, 0.55, 0.40)                       // Grip effects of being below temp,above temp, and off-pressure (higher number -> faster grip dropoff)
    //UPGRADES 
    FrontDryLat=(1.0,1.06,0,4)                             // 6% front grip increase over 9 upgrades
    FrontDryLong=(1.0,1.06,0,4)
    FrontWetLat=(1.0,1.06,0,4)
    FrontWetLong=(1.0,1.06,0,4)
    FrontDrySlide=(1.0,1.06,0,4)
    FrontWetSlide=(1.0,1.06,0,4)
    //FrontCorneringStiffness=(1.0,1.10,0,4)               // 10% cornering/braking stiffness increase over 9 upgrades
    //FrontBrakingStiffness=(1.0,1.10,0,4)
    //FrontSelfAligningStiffness=(1.0,1.10,0,4)
    
     
  12. To be honest, I wouldn't use Shift physics as a base for Racer.
    Shift was a half-assed attempt at a sim, I'm sure a LOT of the numbers were fudged to make cars balanced as opposed to realistic. And I really hope you don't mean Shift 2 hahaha
    That's gotta be the single worst racing game I've ever played.

    To racer though, Ruud mentioned that he might be looking toward the michelin tyre model (or basically a slightly different model that incorporates heat) it might be best to collate a set of tyres after that update.
     
  13. The shift code above was just to show which variables are missing in Racer which could be useful for further tyre physics improvements & also helpful for Ruud/Mitch. Still, what I showed before, using Pacejka to create custom tyres is 1 way of doing tyre stuff in Shift, i.e.

    About Shift 2, it's too soon to talk, the 'official devs' from SMS are checking on Nogrip.com, AFAIK, they gonna fix some of the major issues...to be followed !

    http://www.nogripracing.com/forum/showthread.php?t=248847
     
  14. Shift 2 should be right before release and community/critical consultation. The fact it isn't is worrying. It's not Racer, it's a paid for game :D


    As per the curves. Racer used curves like that back in 2000 ish iirc. Pacejka moved things on. The new Michelin model looks promising if we get that.

    Dave
     
  15. Knut Omdal Tveito

    Knut Omdal Tveito
    Premium Member

    I guess this has already been posted somewhere, but just in case:

    Pacejka coefficients for Ferrari 328:
    Code:
    a0=1.799    (-)
    a1=0.0
    a2=1688.0  (1/kg)
    a3=4140.0  (N)
    a4=6.026    (kN)
    a5=0.0
    a6=-0.3589 (kN)
    a7=1.0        (-)
    a8=0           (-)
    a9=-0.00611   (degree/kN)
    a10=-0.03224  (degree)
    a11-a14=0.0
    
    b0=1.65     (-)
    b1=0.0
    b2=1688.0 (1/MN)
    b3=0
    b4=229.0   (1/kg)
    b5=0
    b6=0
    b7=0
    b8=-10.0   (-)
    b9=0
    b10=0
     
  16. Just to get these back on here for future reference, here's Alpine's original data:

    Code:
    225/45 ZR 17 on 7" rim, 2.4 bar
    
    ; Lateral force
    a0=1.6
    a1=-38
    a2=1201
    a3=1914
    a4=8.7
    a5=0.014
    a6=-0.24
    a7=1.0
    a8=-0.03
    a9=-0.0013
    a10=-0.15
    a111=-8.5
    a112=-0.29
    a12=17.8
    a13=-2.4
    ; Longitudinal force
    b0=1.7
    b1=-80
    b2=1571
    b3=23.3
    b4=300
    b5=0
    b6=0.0068
    b7=0.055
    b8=-0.024
    b9=0.014
    b10=0.26
    b11=-86
    b12=350
    ; Aligning moment
    c0=2.3
    c1=-3.8
    c2=-3.14
    c3=-1.16
    c4=-7.2
    c5=0.0
    c6=0.0
    c7=0.044
    c8=-0.58
    c9=0.18
    c10=0.043
    c11=0.048
    c12=-0.0035
    c13=-0.18
    c14=0.14
    c15=-1.029
    c16=0.27
    c17=-1.1
    Code:
    195/60 HR 15 on 6"1/2 rim at 2.1 bar
    
    ; Lateral force
    a0=1.3
    a1=-49
    a2=1216
    a3=1632
    a4=11
    a5=0.006
    a6=-0.04
    a7=-0.4
    a8=0.003
    a9=-0.002
    a10=0.16
    a111=-11
    a112=0.045
    a12=0.17
    a13=-23.5
    ; Longitudinal force
    b0=1.57
    b1=-48
    b2=1338
    b3=6.8
    b4=444
    b5=0
    b6=0.0034
    b7=-0.008
    b8=0.66
    b9=0
    b10=0
    b11=0
    b12=0
    ; Aligning moment
    c0=2.46
    c1=-2.77
    c2=-2.9
    c3=-0
    c4=-3.6
    c5=-0.1
    c6=0.0004
    c7=0.22
    c8=-2.31
    c9=3.87
    c10=0.0007
    c11=-0.05
    c12=-0.006
    c13=0.33
    c14=-0.04
    c15=-0.4
    c16=0.092
    c17=0.0114
    Code:
    225/60 HR 16
    
    ; Lateral force
    a0=1.9
    a1=-41
    a2=1210
    a3=2180
    a4=10
    a5=0.014
    a6=-0.023
    a7=0.67
    a8=-0.051
    a9=-0.018
    a10=-0.06
    a111=-2.35
    a112=-0.37
    a12=4.3
    a13=-14.9
    ; Longitudinal force
    b0=1.5
    b1=-5.2
    b2=1190
    b3=26.7
    b4=255
    b5=0
    b6=-0.000093
    b7=0.05
    b8=0.49
    b9=-0.007
    b10=-0.23
    b11=141
    ; Aligning moment
    c0=2.53
    c1=-3.
    c2=-6.6
    c3=-0.56
    c4=-8.9
    c5=0
    c6=0
    c7=0.016
    c8=-0.39
    c9=0.35
    c10=0.014
    c11=-0.014
    c12=-0.006
    c13=-0.15
    c14=0.023
    c15=-0.89
    c16=0.025
    c17=-0.4


    Keep in mind that these don't strictly follow Racer's 89/96 model implementation, where b12 is zeroed out normally (but still listed), for example.

    Also, I'm going to stick my head out and say that the first set is probably the mostly used base in practice and that we usually only really modifiy the first five parameters for each section. Doesn't mean that's the way to go, or the only truth.
     
  17. KS95

    KS95
    RACER Moderator

    Could someone explain what those first five parameters are? I'd like to mess around with pacejkas but it's pretty much over my head via the graphs.
     
  18. From Racer's documentation:

    Code:
    The Pacejka coefficient descriptions and units:
    
    
    Code:--------------------------------------------------------
      
      Shape factor ........................................... A0  
      Load infl. on lat. friction coeff (*1000)... (1/kN) .... A1  
      Lateral friction coefficient at load = 0 (*1000) ....... A2  
      Maximum stiffness ........................ (N/deg) ..... A3  
      Load at maximum stiffness ................ (kN) ........ A4  
      Camber infiuence on stiffness ............ (%/deg/100) . A5  
      Curvature change with load ............................. A6  
      Curvature at load = 0 .................................. A7  
      Horizontal shift because of camber ........(deg/deg).... A8  
      Load influence on horizontal shift ........(deg/kN)..... A9  
      Horizontal shift at load = 0 ..............(deg)........ A10 
      Camber influence on vertical shift ........(N/deg/kN)... A111
      Camber influence on vertical shift ........(N/deg/kN**2) A112
      Load influence on vertical shift ..........(N/kN)....... A12 
      Vertical shift at load = 0 ................(N).......... A13
    
      Shape factor ........................................... B0 
      Load infl. on long. friction coeff (*1000)... (1/kN) ... B1 
      Longitudinal friction coefficient at load = 0 (*1000)... B2 
      Curvature factor of stiffness ............ (N/%/kN**2) . B3 
      Change of stiffness with load at load = 0  (N/%/kN) .... B4 
      Change of progressivity of stiffness/load  (1/kN) ...... B5 
      Curvature change with load ............................. B6 
      Curvature change with load ............................. B7 
      Curvature at load = 0 .................................. B8 
      Load influence on horizontal shift ....... (%/kN) ...... B9 
      Horizontal shift at load = 0 ............. (%) ......... B10
      Load influence on vertical shift ......... (N/kN) ...... B11
      Vertical shift at load = 0 ............... (N) ......... B12
    
      Shape factor ........................................... C0 
      Load influence of peak value ............ (Nm/kN**2) ... C1 
      Load influence of peak value ............ (Nm/kN) ...... C2 
      Curvature factor of stiffness ........... (Nm/deg/kN**2) C3 
      Change of stiffness with load at load = 0 (Nm/deg/kN) .. C4 
      Change of progressivity of stiffness/load (1/kN) ....... C5 
      Camber influence on stiffness ........... (%/deg/100) .. C6 
      Curvature change with load ............................. C7 
      Curvature change with load ............................. C8 
      Curvature at load = 0 .................................. C9 
      Camber influence of stiffness .......................... C10
      Camber influence on horizontal shift......(deg/deg)..... C11
      Load influence on horizontal shift........(deg/kN)...... C12
      Horizontal shift at load = 0..............(deg)......... C13
      Camber influence on vertical shift........(Nm/deg/kN**2) C14
      Camber influence on vertical shift........(Nm/deg/kN)... C15
      Load influence on vertical shift..........(Nm/kN)....... C16
      Vertical shift at load = 0................(Nm).......... C17

    The easiest way to experiment is probably by trying out different settings in the pacejka player that comes with Racer - for visualizing the effects, the graphs are pretty neat and can tell you most of what you want to know about the tyre characteristics very quickly.

    a/b/c0 to 4 are interesting because they have the most pronounced effects on the core charactistic parts of these graphs - initial slope angles, peaks and dropoffs (zero intersection for Mz respectively).



    Now this is all my own understanding of the matter, boiled down to a little crash course on reading these graphs:

    Very roughly speaking, initial slope angles for lateral and longitudinal forces relate to the responsiveness of the tyre, whether it gives you immediate reactions or takes more input to gain significant amounts of grip.
    Peaks are your optimal slip ratio and slip angle points, ie where the tyre returns the most grip for a given load. They occur earlier for aggressive race tyres and later for more mundane tyre designs. If you compare Dave's Murcielago tyres and my Tatra 613 numbers, that gives you an idea of the magnitudes perhaps.
    Past peak, the drop off tells you how far you can go before the tyre looses so much grip that playing around the limit becomes snappy, frustrating versus easy recovery.

    The green curve is basically your steering feedback force - you steer more, gaining you more feedback, until somewhere around optimal slip angle, it dies off. While driving, this is when the steering goes light as you approach or cross the cornering limit, which is the tyre's natural and intuitive way of saying you're close to the edge now.
     
    • Like Like x 1
  19. Might hold some interesting Data, even Pacejka.

    http://www.avonmotorsport.com/resource-centre/downloads

    By the way, you should not thank me but the Vehicle Lead @ SMS (People who worked on Shift and now work in pCARS) for finding that.

    I just remembered the good ol' Racer Community :p , maybe you guys get something out of this data ;)
     
    • Like Like x 2
  20. Thanks for posting the link - Avon have provided this kind of data to download for a long time and it's nice that they keep it updated. I remember the Formula Ford info from the days FSR released his Swift racecar and we looked into it :)