What car are you referring to here?
Im assuming an MK5 GTI with 17" Monza's?
By going up an alloy size you will need to lower the profile of your tyre, so yes. It will make things a little harder than what it is currently.
Spacers do the job nicely anyway, sits lovely on 12mm on the back but rubs on the rare occasion with passengers. As mentioned 10mm would be the most i'd go on the front.
My two pennies worth
