OK... First of all, take a look in this picture...
As you may have noticed, it's a magnificent pic taken from game in its hardware graphics mode... All the 16.777.216 possible colors are plotted in this picture... Except the tyres in external views, for what the game uses the 256-color palette...
What I mean? Even in HW mode, the game uses the SW mode for tyres when using external views (chase/TV)... OK, look at picture again... Noticed that even with slick textures, you may find the grooves in the tyres?
So, you got your answer... All views for SW modes (SW mode and HW external views) will feature those grooves... You won't see them in HW mode from cockpit or onboards...
And you were going berserk for that...
Thanks for sharing your question...
GPGSL-3: Fox race driver and team manager - 2011-2012 Constructor Champion - 2012 Driver Champion
Season 9 - #18 Erick Von Draxeler - #35 Marcus Bongardt