Does that have a 4motion (semi-AWD) system? If it does, you'll want to use the exact same tire size front and rear or you'll wear out drivetrain parts quickly. All limited slip systems assume the same final drive ratio front and rear, so if you mess with that more than just the amount of normal (often uneven) tire wear then you'll have a speed difference across the center differential, etc., which makes everything mechanically wear much faster than normal.

And, if it's just FWD, it would look kinda....stupid..to put wider wheels on the rear than the front.



**I'm no VW expert, please excuse any gross assumptions of what that car has/doesn't have for a drivetrain. My advice still stands though.