hahah WOW that's a massive 5.45% smaller rolling diameter than the standard 245/45s, so the rear wheels are rotating a heck of a lot faster than they should be compared to the fronts, hence why tcs is throwing a right wobbly, it thinks you're in a state of perma-drift!
http://www.willtheyfit.com/index.php?width=245&aspect=45&diameter=18&wheelwidth=8.5&offset=33&width2=265&aspect2=35&diameter2=18&wheelwidth2=12&offset2=20
also, muchos kudos on the insane amount of stretch, you could quite happily put a 315 on a 12" rim!