Another 400 miles ended with a shredded tire, burned out servo & cracked rod end.
So the Hextronix died after 394 miles. It was a motor burnout.
In went the SPT.
The front tires came up thrashed from old age & going offroad.
The decision was made to make a helical front tire like the helical rear tires. Because of the round tread, it couldn't be a simple C program that replicated & rotated an STL file. This one performed 96 boolean operations in Blender to create individually rotated layers, over 6 minutes.
Blender has proven useful for final pass booleans, but it doesn't do parametric models, can't import a scene graph from FreeCAD, or have a model history.
It only took 3 tries & $4 of filament to get it close. They're never the perfect hardness.