225/40/18's

[ainarssems]

You could put them on as long as all are the same size but not recommended, normal size for 18" is 245/45R18. 225/40/R18 would be 6% smaller this would result in higher speedo reading, better acceleration, worse fuel economy and lower car plus I do not think they would look any good. For winter wheels narrower are better but You should look for higher not lower profile tyres. 225/50R18 would be good choice, maybe even 225/55R18 for increased ground clearance in winter but that would give lower speedo reading.