I have 5mm on the front and to be honest i'm undicided, they look better as the fill the arch a little more, but i do feel that with the wider track they follow any divert in the road a bit more but also find my car very sensitive to even a psi or two difference in the tyres hence checked at least twice a week, when all running at the same it handles fine, i will be putting 10mm's on the rear when i get hold of some but may remove them if we get snow.