These Extrme tyres a marked as a 235/40 R18 but in real life they are wider (more like 245). I’d like to use 255 tyres but in this case I must use 8.5” wheels and as I wrote before, it is very difficuilt to find something lightweight and by reasonable price.
I will start by 2 bar cold tyre pressure in front and 1.8bar in rear, after session pressure will be around 2.6 in front and 2.4 in rear.
If track temp is very high, I will reduce pressure even more but usually Im using industrial IR thermometer to monitor correct pressure. I will measure the temp outside, centre and inner side of tyres and if temp in the centre of tyres is higher, I will drop pressure. If it is higher on outside of tyre, I will rise it. If temp is higher on inner edge of tyre, I will add positive camber.