I've got quite a lot of my car physics working fine, but there's a slight little problem, as most of my math sucks.
However, I got a little equation telling how much pressure a tire must be able to handle to not skid during a turn in R radius at V speed. The problem is that that equation requires me to know the radius I'm currently turning in (of the whole circle).

Lets say during last calculation (60 times a second) my car was at the green spot (Coords: ABC), this cycle, it is at the red spot (Coords: XYZ).
Out of those two positions, how can I figure out R?
However, I got a little equation telling how much pressure a tire must be able to handle to not skid during a turn in R radius at V speed. The problem is that that equation requires me to know the radius I'm currently turning in (of the whole circle).

Lets say during last calculation (60 times a second) my car was at the green spot (Coords: ABC), this cycle, it is at the red spot (Coords: XYZ).
Out of those two positions, how can I figure out R?