Another thing you'll start running into at 50 miles is nutrition and hydration issues. Many folks just starting out trying to ride further will need to eat much more frequently than experienced riders who have trained their metabolisms. Many people trying to ride further think they're tired when actually they just need to eat a little something. One doesn't necessarily feel hunger. A good thing to do is to take a couple Clif bars with you, opening the packages ahead of time. Eat them 1/4 at a time, maybe at 1/2 hour intervals. Clif brand bars just because of their excellent durability combined with reasonable edibility. If you feel tired and/or a little sleepy, eat.
You can drink to thirst, but be sure to drink when thirsty. You may need to stop to refill water. Or not, depending on temperature.
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