I have a 2021 Lexus IS 350 AWD with 19 staggered wheels, front wheels 8.5Jx19 ET45 tires 235/40ZR19; rear wheels 9.5Jx19 ET60 tires 265/35ZR19
And I'm already thinking about preparing for the upcoming winter season. I'm considering switching out my staggered wheels for square wheels
Which wheel size would you recommend?
8.5Jx19 ET45 or
8.5Jx18 ET45

 

Definitely the smaller wheel with a taller tire.

 

would this wheel fit my 2021 350 AWD F sport?

 

18-inch wheels have been used on the 3IS in the earlier model years without issue, and as far as I know, the brakes are the same size on the 2021+. So... yeah. It should fit.