I think a 245/70/16 is about 29.5inches, probably closer to 29 when measured which means you've gone up about an inch in height and close to an inch in width. Realistically you probably wouldn't notice the difference on the road. I went from 225/75/15 (28 inches) to 30/9.5/15 and haven't noticed any difference on or off the road gearing wise. I would probably go to 31's if I had more room under the guards (3 inch lift on its way) but wouldn't go any bigger without planning to regear.
31's probably won't rub in normal driving but don't try tight u-turns, my 30's just fit... Offroad 31's will rub all over the place :(
If you want a cool little VB (not the beer) application I wrote to compare tyre sizes/rpm/speed etc go to
http://www.baja.com/kombi/bustech6.htm and download, let me know what you think.
Cheers
Steve