225/45/17 is not only wider, but also taller than 215/45/17. Its deceptive because both list the height as 45, but you have to realize that that number is a ratio of the width, and consequently will be taller with a wider tire. You can go to tire rack or any tire manufacturer's website and see the spec for individual tires. It shouldn't affect your speedo more than a 1-2 mph at 60.
