Hi, I have a G31 540i xDrive, and had some lightly used18 inch alloys, with Goodyear Ultragrip 8 winter tyres, delivered. All the wheels are the same size, but my summer 20 inch alloys have larger rear wheels. My tyre fitter says being the wheels being the same size for winter tyres is not a problem, and may even be advantageous. Is it standard practice to have all winter wheels the same size? Hopefully to give something back, I can advise anyone looking for a set of winter alloys not to go below 18 inches, if they have M Sport brake callipers; 18 inches just fitted; phew!