after implementing a mod in the newly installed GP4 I discover at once white tyre treads.. how to get rid of them resp. turn them to black ("paint it black" - the rolling stones - one of my favourite songs ).
well, I think that was it - I solved the problem creating a mclaren_tread_0_right_0 and so on, put it in the tyres-folder of the mod and it worked fine - thank you mate