BMW 640i GT xDrive tire size
The most common factory tire size for the BMW 640i GT xDrive is 245/40R20 front, 275/35R20 rear, on 2 of the 2 year and trim fits listed. The table lists every year from 2018 to 2019 and the size each trim was built with. Pick your year and trim to see the tires that fit.
Check your own tire
A trim can be sold with more than one wheel size. The size printed on the sidewall of your current tire, or on the placard in the driver's door jamb, is the one your vehicle has.