[crles2]

Can I mount 225/45/17 snow tires (not run flats) on the stock rims on my 2023 330i Xdrive with 225/45/18 run flats, and be safe and secure with this? Do I need new rims? Do I need to get snow tires that are 225/45/18?

[pdxtiger]

You have a little wiggle room on tread width and ratio, but wheel diameter is wheel diameter. You either need to get R18 (18" diameter) tires or a different set of wheels. Narrower wheels and tires are better for the snow if you choose the latter option. Michelin X-Ice, Blizzaks are solid options. Nokians are king.