LARGER tire size on an XC60 for offroad use?

[prendrefeu]

Hello!

I've been taking my volvos off-roading more than most 4x4s would ever go, and my current XC60 (AWD, with various minor off-road-ready mods) thrives quite well out there. That said, I'm looking at new tire options when my current Pirelli (plural?) finally wear down. The current tires are stock 235/60r18 tires, and after some searching I've read that an alternative size would be 245/60r18

I know that going a size larger would:
-give an extra inch of ride height
-throw off the speedometer and MPG calculations (+1 on the speedometer and probably make the MPG appear less)

Are there any other downsides? Would these even fit, or is there a chance that they would hit the tire well when I'm turning? It seems visually at least, that the clearance would be tighter but still pass just fine without any rubbing even at the most extreme of tire angles.

Has anyone else tried this?

Either way - any thoughts on having some decent off-road/all terrain tires fitted?
I'm looking at Continental's offerings of the TerrainContact A/T and Yokohama's Geolandar A/T series.
Any others?

Thank you.

[Rattnalle]

Apart from the car being built as a city car I'd look i to smaller rims. I'm sure you can get something more appropriate than 18" on there. The more air between ground and rim the better.