Originally Posted by tarwheel

If you have been regularly riding 20 miles/day, you are probably fit enough to ride a century. However, you will find the century much more enjoyable if you can schedule some longer training rides in the 40-50-60 mile range before tackling the longer distance. Riding a century simply take a lot of time and it helps to get your body used to the extra time in the saddle. There is also the mental aspect, which you shouldn't underestimate. Once you get past 60 miles, it takes a certain mental toughness to keep going if you are not used to riding longer distances. Scheduling some longer training rides will also help you work out any kinks regarding bike fit and equipment.