Tyre Size Question

[Byr0n]

Hi guys, just bought a 2005 B6. The wheels on the car are 215/55R16. Is it possible to change all the wheels to 205/55/R16's ?

The back two need changing. Can I change the back two to 205's and leave the fronts as 215's or would you recommend changing them all to avoid any potential ABS lights flashing up

Thanks