The XC40 T5 was available from the factory with 18-inch wheels with 235/55R18 tyres, so there should be no issues assuming you fit the correct factory alloys in this size. Your 19-inch wheels are likely wearing 235/50R19 tyres, so an alternative could be to switch to 55 profile tyres on your 19-inch wheels. This should offer a small increase in ride comfort, and would be a cheaper option than a new set of wheels and tyres.