I had a similar kind of experience with the tires in New Zealand as in the OP. I was battling for the win with the AI. Just two stages to go, and I was in second place just a second behind the leader. The first stage was a long one (over 12km) and the second was a short one (4km). Game suggested me medium tires, but I decided to gamble, and went for the soft ones. It was a risk worth taking. Absolutely hammered the AI on the long stage, and grabbed a stage win by 40 seconds. Of course my tires melted down on me, but because the last stage was so short, I lost only 5 seconds there, and managed to win the event.