TIRES SIZE s70
 

does anyone know the largest I can go on 15 inch stock wheels without rubbing.I know 205/50/15 will fit,but what about 225/50/15

Recommended tire size is 205/50 or 55/16, 205/55/15, 195/60/15.
225/50/15 is too large.
Except for the possible interference with the wheel house, you will experience very sluggish move and worst mpg in low or middle speed range.
Volvo cars handling characteristics are usually exceptionally sensitive to tire sizes.
You will probably lose its own handling characteristics with too large tires.

I just tried bigger, 205/60 and went back to the standard 195/60 R 15 which I felt worked best