If I decided to get 19 inch (OEM Polestar) wheels for my 2018 S60 Polestar and want the closest 19" tire size to the OEM 20 inch setup:
I see the tirerack size 245/40-R19 is closer (negligeable 0.13% speedo error) than the Polestar rep size (235/40-R19) which has 1.33% speed error. Neither has any poke or inset issues.
I assume the Polestar rep was responding based on available sizes for 'winter performance' tires for the 19 inch (winter) rims and hence did not suggest the closer 245/40/R19?
Any reason to get Polestar rep's (winter) size 235/40-R19 instead of Tirerack recommended 245/40-R19 size given OEM 245/35-20 size, assuming I am getting UHP all season tires (and not winter tires) for argument's sake. (edited message due to size typo - I flipped the two sizes in this particular sentence by mistake).
Tirerack 19 inch tire size
Polestar Rep 19 inch tire size when asked for 19" winter tires (for 19 inch OEM rims):
Used ET53 offset and 8 inch rim width.