I’m not sure what tires you use but if you have some lab data you can fit it (even full blown MF 5.2 if necessary). The Pacejka4 model does a really good fit to most tires , but race tires have a special operating region that can require a weighting function along side slip angle data. No problems usually with load data. Race tires like load.

Here’s the Pacejka4 code (Matlab basis). It woks for Fy, Mz, Mx, Fx, etc. Watch your signs. Input units are degrees and +Newtons. If you have Matlab, I have some Pacejka4 GUI demos of usage in vehicle modeling (Mostly FSAE).

Here are some coefficients to play with:

Hoosier 225/45R17 248 kPa 9″ rim.

Fy Mz Mx

D1 1.4647 -.00012504 -.01142

D2 .041123 .0036391 .0023342

B .22715 .38321 .07409

C 1.6031 2.3602 2.5811

I hope I got it right, if not I’ll send a snippet from the fitter.

BTW: how do you post a picture (.jpg) on here ???

function fy = Pacejka4_Model(P,X)

% x1 = X(:,1); %Slip

% x2 = X(:,2); % Fz

% D1 = P(1);

% D2 = P(2);

% B = P(3);

% C = P(4);

% D = (D1 + D2/1000.*x2).*x2; % peak value (normalized

% fy = D.*sin(C.*atan(B.*x1));

% x1 = X(:,1); %Slip

% x2 = X(:,2); % Fz

% D1 = P(1);

% D2 = P(2);

% B = P(3);

% C = P(4);

D = (P(1) + P(2)/1000.*X(:,2)).*X(:,2); % peak value (normalized

fy = D.*sin(P(4).*atan(P(3).* X(:,1)));

thank you very much for your comment. It is amazing to have you commenting here!

I can immediately say that the purpose of this simple tool is much easier than what you describe, because more than being something able to characterize the car in terms of typical vehicle dynamics terms (steering gain, response, connectedness, understeer gradient, etc), it mainly something aimed to investigate only the overall performance envelope of the car, under the given assumptions (both in terms of solver and given data).

Indeed, setup parameters influencing which axle saturates first in something which should resemble a constant speed / reducing cornering radius test come into play, because this is the way i extrapolate the maximum acceleration the car can achieve at each velocity step. I repeat this procedure at speed ranging from very low to very high (depending on car type) to detect how car’s behavior change depending on downforce. Anyway, the tire model is extremely simplified and i don’t consider any compliance in suspension or steering system, as this is already beyond the scope of this simple tool.

In any case I would be extremely interested in your input about what you describe. I would be more than happy to get in contact to discuss this further.

Thanks again for reaching out here!

]]>If you are interested, I can both send you model parameters (linear & nonlinear tires and steering systems) and show you how to analyze YOUR vehicle models. All my stuff is in Matlab and I can read in spreadsheet material with it. For tire data, I can give you a 4 term Pacejka-Lite model that can even be turned into a perfectly linear representation for diagnosis purposes.

This process is called ‘validation’ and gives credibility to your efforts. If the vehicle model is NFG, then your efforts are a waste of time. You might be surprised at how good your model(s) are or the other way around. Plus you might surprised at how handling characteristic terms have good engineering descriptors that your whole team will need to step up to if they are still all hand-wavers. This ‘New School’ racing ! I sure hate to see valiant efforts wasted on classical mistakes made in unknown territory…

]]>thank you very much for your kind words! I really appreciate it.

I am sorry, but the file is not public and i am not planning any release or purchase in the short term.

It is more of a tool i use for my own projects and something i use as a learning exercise.

]]>This project is exceptionally interesting, and the changes you have made seem to have brought it to a whole new level!

Is a version of the Excel file available for download or purchase to investigate for interest (with restrictions of course)?

Kind regards

]]>Please also check my work From Team Traffic Racing ]]>

not planning to give the tool out for now.

I did this simple tool mainly for myself and for my projects, haven’t planned any public release for now.

]]>I’m a race engineer….and use to develop different tools for my job…

Thank you

Fabio Gentili

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