245/45R19 front, 275/40R19 is what you want.
Your combo is 2.4% off, whereas 245/45R19 and 275/40R19 is 0.1% off.
And your car isn't an X3m. It's an X3 3.0si with M-Sport package.
Could a mod please move this out of the X3M Forum and into the proper forum?