can I replace the 225 45 17 tires on a 2011 328I with 215 55 17?

the specification on the doorjamb is the key to proper handling...do not stray from this tire size...your insurance company should be told that you are not runnin' with the engineered size~

I agree with judge_roy. they will probably fit tho. But will be noticeably shorter in height and narrower in width. Probably would not look right and would handle different from the originals. I would not advise making such a dramatic tire size change.

use this tire size calculator to compare the size of the tires.http://www.miata.net/garage/tirecalc.html and there is no reason for your insurance company to know anything about your tires. make an informed decision and talk to a tire shop. they can probably help you find a size that will work. do not pay attention to those that are afraid of anything other than stock.