Is anybody out there running a 245/45 on 16" wheels and if so what offset, trying to see if it's plausible to run them on my r53 with 16x8 enkei rpf1 et38.

 

245 width is extremely aggressive for the Mini. I have known people to run 235's on 8" and get them to clear... in 17"

 

245/45-16 fits wheels 7.5-9" wide, perfect for 8" wide rim so it will fit the 16x8" rim fine.

What suspension? If stock then there is some clearance but not much. If you are lowered then you should be prepared to use lots of negative camber especially in front with adjustable front camber plates set to max negative and trim the black plastic wheel arches as needed.

Compared to OEM 16" wheels, the 16x8" et38 is aggressive and sits 9mm closer to the inner suspension strut and pokes out 29.1mm more.

So you really have little to no room with a dropped suspension and you might even need a thin spacer in the rear depending on how much inner rim clearance you have for the rear lower trailing arm. The more the drop the less the clearance so if you have fully adjustable ride height then you can use that for some wiggle room.

On my R53 with 1.5" drop, using 15x8" et36 wheels the inner rim touches the rear trailing arm requiring a 3 mm spacer. Your 16" wheel has a larger diameter radius but it could be close, you do need some gap for air cooling.

Overall I think it can be done but you need to be aware you might have to do a few things to avoid rubbing.

On a long track using a tire size this large is OK, but for autocross and short track we tend to use tire sizes giving a smaller 23" or similar tire diameter for lowered gearing since the R53 transmission (getrag) is a little taller in low gears. This allows for slightly better lower speed acceleration but might reduce top end speed.