Fuji Speedway
 

The fastest setup at Fuji Speedway is 265/35r18, on 9.5J rims, with 5.1 final-ratio and close-ratio 6th. We use Kumho V70a K61 compounds, and have low-drag GT-wings (e.g. pro-composite). We have no PWR... just headers and intakes.

I run 245/40r17 on 9J rims, with 4.8 final-ratio and stock 6th, to manage costs... for now. It is about 0.5sec to 1.0sec slower compared to the fastest setup.

Once you start to really push, 265/35r18 is the fastest setup even on a high-speed track like Fuji Speedway.