When does food become available?
 

In other words, if I want to ride at 3pm, when should I be eating which sorts of foods?

How far and how fast? If it's less than forty miles/two hours, don't worry about it at all. Just make sure you have some water with you.

I don't think OP is asking what to eat while riding, but what and when to eat during the day before riding.

Some people don't like to eat right before riding, or even up to a few hours before riding. I figure if I eat while riding then eating before riding shouldn't be a big deal, but you want to eat foods that are easily digestible. Also goes for food while riding.

I would definitely agree that it depends on intensity as well. I am more sensitive to what I eat before doing intervals than before a long endurance ride.

As for intensity, Im old and fat and trying to get back in shape. Me going uphill is like a tractor pull... everything is intense.
SO after an hour or so, I start to wane, "bonking".. I think its called.

I was just wondering about eating for endurance. I think maybe I should just keep riding....

If you start to wane after an hour (yes, bonking), eat something in the 200-300 calorie range. It really doesn't matter what, as long as it isn't something that is going to sit in your stomach like lead or be too spicy. As you ride longer distances, aim to eat about 200-300 calories per hour.

Yes, as you get fitter you can get away with eating less, but it is good to start out eating 200-300 calories per hour, so that you do not bonk and so that you can ride longer distances.

Ah, OK. In that case I think the answer is to eat something suitable before you start. Complex carbohydrate, not just simple sugar. Oatmeal and a banana an hour before you start would be good, for example, but even sandwiches would be OK . Then while riding, follow machka's advice above. Energy bars are convenient and you can see exactly how many calories you're eating, but dried fruit works - whatever, as long as you can digest it easily.

Okay. I like granola bars and dried fruit. I can manage that.
So what about protein? How is that metabolized?

Slower than carbs.

It's good to consume protein on long rides (i.e. centuries) but for shorter rides, it isn't necessary. However if you do a hard ride, you might want to eat something after with a 4:1 ratio of carbs:protein for recovery.

I normally ride in the morning and eat before then.

The meal before a ride should be low GI - so that your body will take time metabolising it and it will give you energy entering your blood stream over a period of time. Eating high GI food would give you a sugar spike - and then it's gone (which is great while you are riding).