I ride a Kona CX bike with 700x35 tires on it. I can't remember off the top of my head what the tires are, but they are semi-slick, and very nice on-road, and fairly decent off-road. I'm not sure how nasty the off-road portions of this race are going to be, but if it's not any worse than packed dirt / gravel / light mud the semi-slick types are a nice compromise between road speed and off-road stability. I used this bike primarily as a road bike (with some fast packed-dirt trail riding thrown in) for a year, until I got my raleigh.