To big in what way? Recommended is 225/45/17 so the circumference and diameter will be more (2066 vs 1991 mm and 658 vs 634 mm), meaning that your speedometer will be 3-4 % off. Your actual speed will be a little bit higher than what the speedo shows. But they will fit in the wheelwell, can't imagine these extra few mm's will be a problem.
As for width in winter conditions they are perfect. FYI, I ran with snow tires 225/40/18 fronts and 255/35/18 rears. No problem.
Will they be fitted on a new set of rims? And if they will be what is the size of these rims (width and ET) and are the OEM? If they are OEM what partnr. or from which model? If they go on your current rims I can't see any problem.