Hello Everyone,

My name is Nils and I am a current member of the chassis group on Michigan Tech's FSAE Team; I'm new to tire analysis, and not incredibly proficient with Matlab, so pardon the rookie questions.

I have been trying to effectively generate Fy vs. SA curves to analyze tire characteristics, both to make an informed decision on tire compound (R25B vs. LC0), and to optimize camber gain, and have tried the following approaches.

- I have gotten the mrandim matlab code provided by the TTC to run for rounds 1-3, but since not many 10in tires (the tire size our team uses) were tested in this range, it is of limited use for us as I am most interested in round 5 data. I have downloaded the code provided by Bill Cobb but have not made significant progress getting it to run.

- I imported the TTC raw data into excel, and plotted SA vs. Fy manually for different Fz loads. However this process is very tedious, and somewhat inaccurate since the data is not a smooth line. In theory I could put a higher degree polynomial best fit line on this plot, and subsequently compare a plot of these best fit lines for different tires/different Fz's?

- In searching for additional resources online, I found an MFeval matlab code (https://www.mathworks.com/matlabcent...e/63618-mfeval) which evaluates magic formula 6.1.2 with provided coefficients in a .TIR file. In going through older TTC threads, I was able to locate the .TIR files for rounds 4 and 5 on that forum (round 5: http://www.fsaettc.org/viewtopic.php...hilit=tir#p717), however the file does not seem to have all the coefficients which this program needs to run. I copied in the following coefficients over from a .TIR example file provided with the code, and got the code to run, but the plots are not right, which makes sense since the coefficients are not correct for the given tire.

Sorry for the long post; does anyone have advice on how I might better evaluate this data and get the results I'm looking for (SA vs. Fy plot at different Fz loads/camber angles)? Unfortunately our school does not have access to OptimumTire.

Thanks for any and all advice!


Below are the additional coefficients which I needed to copy into the TTC TIR file to get the MFeval program to accept it:

$-------------------------------------------------OPERATING_CONDITIONS
[OPERATING_CONDITIONS]
INFLPRES = 68947.6 $Tyre inflation pressure
NOMPRES = 68947.6 $Nominal tyre inflation pressure
$---------------------------------------------inflation_pressure_range
[INFLATION_PRESSURE_RANGE]
PRESMIN = 65000 $Minimum valid tyre inflation pressure
PRESMAX = 75000 $Maximum valid tyre inflation pressure
PFZ1 = 0.8260162 $Pressure effect on vertical stiffness
Q_RE0 = 1.00093 $Ratio of free tyre radius with nominal tyre
Q_V1 = 0.0007860039 $Tyre radius increase with speed
Q_RA1 = 0.4998311 $Square root term in contact length equation
Q_RA2 = 1.426644 $Linear term in contact length equation
Q_RB1 = 1.297038 $Root term in contact width equation
Q_RB2 = -1.500634 $Linear term in contact width equation
PPX1 = -0.9782748 $linear influence of inflation pressure on
PPX2 = 0.5317977 $quadratic influence of inflation pressure on
PPX3 = 0.002880684 $linear influence of inflation pressure on peak
PPX4 = -0.2125442 $quadratic influence of inflation pressure on peak
LKYC = 1 $Scale factor of camber force stiffness
PEY5 = -3.982573 $Variation of curvature Efy with camber squared
PKY4 = 3.193074 $Curvature of stiffness Kfy
PKY5 = -15.40705 $Peak stiffness variation with camber squared
PKY6 = -1.110033 $Fy camber stiffness factor
PKY7 = 0.3001414 $Vertical load dependency of camber
PPY1 = 0.4216594 $influence of inflation pressure on cornering
PPY2 = 1.095625 $influence of inflation pressure on dependency of nominal tyre load on cornering stiffness
PPY3 = 0.07316054 $linear influence of inflation pressure on lateral peak friction
PPY4 = -0.197418 $quadratic influence of inflation pressure on lateral peak friction
PPY5 = -0.7908439 $Influence of inflation pressure on camber
LKZC = 1 $Scale factor of camber torque stiffness
QDZ10 = 2.05206 $Variation of peak factor Dmr with camber squared
QDZ11 = 5.083876 $Variation of Dmr with camber squared and load
PPZ1 = 0.8313204 $effect of inflation pressure on length of pneumatic trail
PPZ2 = -0.1946372 $Influence of inflation pressure on residual aligning torque
RBX3 = 19.90875 $Influence of camber on stiffness for Fx combined
RBY4 = 89.98708 $Influence of camber on stiffness of Fy combined
QSX4 = 0.1527435 $Mixed load lateral force and camber on Mx
QSX5 = 14.81053 $Load effect on Mx with lateral force and camber
QSX6 = 10.68144 $B-factor of load with Mx
QSX7 = 7.215284 $Camber with load on Mx
QSX8 = -4.145403 $Lateral force with load on Mx
QSX9 = -0.3814996 $B-factor of lateral force with load on Mx
QSX10 = -2.530221 $Vertical force with camber on Mx
QSX11 = 36947.57 $B-factor of vertical force with camber on Mx
QSX12 = 0 $Camber squared induced overturning moment
QSX13 = 0 $Lateral force induced overturning moment
QSX14 = 0 $Lateral force induced overturning moment with camber
PPMX1 = -0.05338798 $Influence of inflation pressure on overturning moment
QSY4 = 4.0E-5 $Rolling resistance torque depending on speed ^4
QSY5 = 0 $Rolling resistance torque depending on camber squared
QSY6 = 0 $Rolling resistance torque depending on load and camber squared
QSY7 = 0.85 $Rolling resistance torque coefficient load dependency
QSY8 = -0.4 $Rolling resistance torque coefficient pressure dependency
Q_V2 = 0.01985276 $Vertical stiffness increase with speed
Q_FZ2 = 14.85126 $Quadratic term in load vs. deflection
Q_FCX = 0 $Longitudinal force influence on vertical stiffness
Q_FCY = 0 $Lateral force influence on vertical stiffness