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car.ini > Tires

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:
 
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.
 
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.
 

Attachments

  • pacejk.7z
    99.7 KB · Views: 717
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.
 
@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.
 
pacejka01.jpg


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...:)
 
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.





Uploaded with ImageShack.us
 
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)
 
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.
 
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
 
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
 
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
 
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.
 

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.
 
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.
 
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 :)
 
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