DO NOT!
I repeat - DO NOT put 45 profile tryes on 17 inch wheels for a Mk3!!!!!
The correct profile is 40.
My 17's certainly do not look big on my car! Wayne's opion is wrong as usual.
However I do say that 17 x 40's do give a little harshness on the ride quality front. But then I do have the stiffness of my dampers wound right up!