aparently with those tyres they'll go straight on, but I'm thinking the same as you my friend and my 15's are getting pretty close to the arches when I have people in the back.
I think G60 arches and getting them rolled is a good idea. gives a bit of leaniance when you load the back up (if you ever do) or jump into a drop in the road going a bit too quick

I've heard it's about ?80 to get them rolled, but don't hold me to that.
