Go to this website and enter in the 2 diff tire sizes you're considering, it will then tell you the various differences that would occur. In the 2 you mention, the 245 would be 1" larger diameter (remember, the 'profile' is an 'aspect ratio' and is calculated as 65% of the ties width (so changing width but same aspect ratio number means the profile will change, in this case resulting in 1" in diameter increase).
As Rygrego points out, a 245/60/17 would be a much better match. Virtually the same in diameter, thus little to no difference in speedo etc.
One other thing to keep in mind would be the oem rim width. If you keep the same rims (you didn't mention new rims), then you'd be putting a 245 width tire on a 6.5" width rim. That is going to look horribly pinched. Which may be fine by you! Some people like that look. But know ahead of time, the recommended 'maximum' tire width for a 6.5" width rim is a 215 (and even Honda puts a 225 on it!).
It would have the look of a 'mudder', which sounds like you may be wanting.
Over at Tirerack.com they show only one 245/60/17 tire option.......it's a $220 Michelin and it is not an offload tread. The rim width range for the 245/60/17 shows 7"-8.5".
If you went to a 235/65/17 size tire, there would be way more tire choices/options and the 235 would be closer to the original diameter, and diameter is the most important number. The 235 size also shows a 6.5" rim width as being acceptable.