Originally Posted by
banerjek
Riding 100 miles requires far less fitness, strength, etc than most people think. What it does require is pacing. When you ride, your legs still need to feel fresh at the 50 mile mark. This means that you need to ride at a speed that feels easy or even slow.
+1.
I think a good test is if you can do a reasonably vigorous 50 mile ride over similar terrain without feeling too exhausted the next day. I don't think it would be wise to try 100 without trying 50 first.
If you can do that, I'd recommend going very easy over the first 50 miles of the century, and not pushing yourself AT ALL. I'm talking about riding 1-2 MPH slower than the speed that you did on your 50-mile test ride, and be sure to use a relatively high cadence so you're not straining your legs. If you feel good after 50 miles, you might speed up a little but not too much. Later in the ride it will require increasing amounts of perceived energy to go the same speed, and you'll be suffering by mile 90 if not before.
As others have said, it's very important to drink plenty and eat plenty, and keep up your electrolytes.