Thanks for your help. I guess I need to understand the whole thing much better. I haven't deleted any files yet. My sdk files are a few weeks old so I haven't checked for updates yet. As for the road mesh size, I already tried it but the surface didn't have any friction then > spinning wheels (same material name, same mesh name, same export settings) and I vaguely remember that about the tdf file so i just tried it as an act of despair . I'm going to test your suggestions later on this day.
Guys, I got it and the art was perfectly set up as documented. My Real Road Scale in the options was set to Static. I really thought, the road starts wet, when rain is set as session condition and I just haven't had this option in mind anymore. However, with a scale of 15 I can finally see a change from dry to wet. The LOD setting for the car worked fine btw but later I'd like to use the lods again. Anyway, that's fine for now.
