some more work on the tires.
found a little trick using .obj export to join meshes:
Something frustrating in .kn5 transition is to join individual object together for optimisation. Once joined, they sometimes lose the uwmapping and they are much more difficult to modify or move afterward you have realized it's not yet okay in AC... Tires stack are the perfect example. I prefer to keep them as individual object in my rhino file.
i found out that when exporting to obj format, there's an option to group meshes by name.
so i renamed all my white tires to a single name, same thing for the red ones, export them to obj, reimport them back into rhino: i have now two meshes, one for the red and one for the white tires. and the texture mapping is now baked.
then i split those meshes in two or three group so it does not exceed 30 000 faces.
it creates a dupplicate,but my working file stays flexible.
Anyway, hopefully i won't redo them again.