Just curious how many of you do a significant amount of training on a road bike. I'm in the process of buying a mountain bike and training for a 100 mile race and perhaps a 12 hour solo. It seems like a lot of people do a big chunk of training on the road. However I can not afford to buy two bikes. Will I be able to have a quality training program without including a road bike? I read somewhere Tinker Juarez trains 4 out of 6 days a week on a road bike.