how big can i go with a set of rota alloys i was thinking of putting a set 18.inche rims on but not to sure about tyre size i did want to add a set of arches aswell

I've got 17" rota boosts on my v1 sti and I think size wise they're ideal . As they fill the arches well enough but don't comprise traction in the twisties or chip my teeth on speed bumps .

As if you go up to 18's you have to get a lower profile tyre to keep the rolling radius the same .

17s work best on a classic in terms of looks and handling