yeah you need 7.5 width with the 18s, i had no bother getting these, if you go for 8s youll loose full lock and suffer from a lot of rubbing in the corners
It depends if the speedo is inaccurate to begin with.18's will make the speedo read more accurate than the standard 16's
and the ones off the r32 golf will be too wide
make sure the width of the wheel is less than 8. As i had rs4 genuine wheels on mines and tyres where catching front wings.
Either that u put a very low profile tyre on it.
I had 224/40/18.
So i'd go for 7.5 width on an 18 wheel which could be hard to find