What's the limitation on tire width?

Hey guys:I've been trying to figure this out and thought I'd throw it out there: I've got a Honda Element and I'm due for new tires, and I wanted to go wider than stock. Does anyone know how to figure out how wide I can go on the existing rims, or what the other limitations may be? I'd be ok with losing out on turn radius since it'll rub on the inner wheel well earlier in the turn, but can't think of a method to figure out what max room is.It's already sporting +1 OEM sizing (225/17/75r i think). It throws the speedo out of whack a little but I've had no other issues, and it's been nice to have about an inch and half additional ground clearance from stock. I wanted to go something like a 245 70r or thereabouts, like the size of a rear Corvettes.Management appreciates your opinions.