spokenword

I can say from experience that 15 miles, by itself, without anything longer, won't get you to a century. You need at least a 40 or 50 mile ride in there to get some mental conditioning for the hours in the saddle and the way your body reacts as it experiences more fatigue. The physical fitness part is only half of the training equation.

Carbonfiberboy 

No, it was a solo ride, just for fun and to see if I could do it in 6-1/2 hrs. which was reputed to be the time of a female track and field athlete who was training for the next Olympics. Being 18, I figured if a girl could do it, I could do it, so I did it. By trashed, I mean I could hardly make it up the stairs to my apartment when I got back. I was real tired and undoubtedly dehydrated. And no, that's not an example to follow, but it does show what a young guy can get away with. Was it Penseyres who rode 276 miles (or something like that) without any food or water whatsoever?

Machka 

However, once you've got several dozen centuries under your belt, you get to the point where you can just go out and do a century with very little prep ... for example, you can take a month completely off the bicycle, and still go out and ride a century. I think it does have to do with mental conditioning, and prior knowledge.

spokenword

true. I should've qualified my previous statement by saying that, for a newcomer, it would be unrealistic to think that you can ride a century simply because you've been putting in a regular set of 15 mile weekdays.