Granted different tyres but 205/45/16 and 195/50/16 was night and day. The 195s were so long, would be okay for a turbo. Thats why I ask, because the 195/50/15 seems too small195/50R15 will be a cheaper tyre, which is the main motive for moving to 15 inch wheels.
As far as changes to the rolling radius of the wheel go, I'd be very suprised if you'd be able to tell. https://tiresize.com/calculator/
@robmuns what site is that you're using?
Thanks Ive used that site before. I was more after real world experience on track, but would be nice to drive it on the road without being at 4k+ barely going 70