In reply to CarbonCopy:
I've done this race twice and firstly it's a great race, you'll love it. Depends if you want to compete or complete. I used my specialised tricross which worked fine and was pretty quick but if you want to compete at the front you'll want a road bike as nearly all the biking is on roads or good gravel roads, only two short mountain biking sections which you could almost run the bike down if needed. If I did it again I'd definitely use my road bike as probably 20% faster on the long road sections. I repeat, really fun race, the one day probably edges the two day as a memorable event.