I search but I don't found anything about it, sorry if had mentioned before.
I have a shifter kart and I notice with it that the race line is important not only for make less meters or going fast, also for the rubber on it.
A day with out rubber in the track (after a rain day) I race 3 seconds slow than a day with rubber. (A good lap is 1m08s)
I don't see any racing simulator that has this important (and realistic) parameter, the track never is the same, every day changes.
Also I see on the Formula 1 show, showed by Pedro de la Rosa (McLaren test driver) how when he walk on foot on the rubber, the camera and the microphone picks up the sound of his shoes coming off of the rubber of this race line.
So that rubber is very sticky and can improve the handling a lot of more than the kart tyres ...
At the same time, remnants of scrap rubber go outside of this race line and it is like stepping gravel
Will be a good complement with the new tyre model physics
Also humidity or ambient temperature affects to tires and engine, and you can race fast easly with a cloud moment than a sunny moment in the same day... but this is another thread