Yeah, OE tire should be 235/55/18 and if you go with 225/60/18 for winters it is only 1.7% bigger in wheel diameter so should not be an issue.
However, if your OE is 225/55/18 and you go with 225/60/18 then new tire will be 3.1% taller. Still under 4% which I hear is the what you do not want to exceed.