MX Bikes Official Forum

Hi all,

I've made a little tool to visualize the tyre model (Magic Formula) used by GPB. If you don't know what the Magic Formula is, the tool is *not* for you :)

NOTE: the tool is very much beta. The equations involved are messy and I cannot grant an error has not slipped in. If anybody with knowledge of this stuff wants to double check, that would be appreciated. I can send you the relevant source code for that, just PM me. Of course, if Piboso could validate all that, that would be ideal (but he probably has other things to do).

It can load two set of parameters (two .tyre files) to compare and modify them (only the Magic Formula parameters). It has 4 tabs, one for each graph:

• Longitudianl force: as function of longitudinal slip (x axis) and of vertical load, side slip and camber (sliders).
• Lateral force: as function of lateral slip (x axis) and of vertical load, longitudinal slip and camber (sliders).
• Aligning torque: as function of lateral slip (x axis) and of vertical load, longitudinal slip and camber (sliders).
• Lateral force vs Longitudinal  force: as function of vertical load, side slip, side slip and camber (sliders). Line is plotted for longitudinal slip between -1.00 and +1.00.

Any time a value is modified, the graphs are updated. Same any time a slider is moved. Double clicking on a slider will bring it back to its default position.

On each graph there are 4 lines: 2 for the 1st model (in blue), 2 for the second model (in red).
On the longitudinal force graph (for example), it draws (for each model) the line with zero side slip and zero camber (dashed line) and the line with the values of side slip and camber specified by the sliders.

Using shift+mousewheel and ctrl+mousewheel you can zoom in/out of the X/Y axes. shit/ctrl+drag will pan the X/Y axes. A double click will zoom out to full graph.

(https://i.imgur.com/43H2Q2R.png) (https://i.imgur.com/43H2Q2R.png)

DOWNLOAD v1.6b (2017/05/16) : (https://mega.nz/#F!dBlW1SIZ!t4J1IooPK-hNpSpm0K_ZQg) <<-- THIS if for GPB beta9/10/11 and MXB beta5/6 (subsequent versions TBC).

INSTALLATION: this is not a plugin, it's a standalone tool. Just copy it in a folder where you have write rights (i.e. avoid "Program Files" and similar). The sample files provided are the ones of the 3 default bikes in GPB beta8.

IMPORTANT: in case of issues like missing dlls or things not showing up, please install Microsoft Visual C++ 2015 Redistributable Package (x86). It's available in the .zip (vcredist_x86.exe) or you can download it at https://www.microsoft.com/en-US/download/details.aspx?id=48145 (https://www.microsoft.com/en-US/download/details.aspx?id=48145) (download the x86 version, "vcredist_x86.exe", not the x64 version).

v1.6 out:

• Option to avoid writing to the .tyre file the parameters with zero value (makes the file smaller and easier to read).
• Color coding of parameters in the table: red if modified with respect to the loaded file, black unmodified, light grey if zero.
• Menu command/shortcut to reset an entire model to its original parameters.
• Fix the legend (one numeric value was wrong, 0.00 instead of 1.00).

NOTE: if you open a .tyre file in MaxTyre, and then save it without changing anything, the order of the parameters in the saved file may be different from the original file.
To be honest I don't know if it makes a difference online (file mismatch), but I suspect it does.

If you want to easily double check nothing has been changed, I suggest a good diff tool (e.g. Notepad++ + it's compare plugin).

Even with the tool, you still probably need a book to understand what the curves are :)

v1.6b out:

• Fix a monster of a bug i cannot even understand how I missed it. Thx to Loopateli for reporting.