Originally Posted by Radish_legs

Do you not have a group ride in your area that an simulate a road race? We have 3 or 4 in the Dallas area that would qualify. Then you could experiment. Does it happen? What can I do to prevent it? Probably your hydration status is insufficient. If you don't have such a group ride, add intervals in your long ride that would mimic what happens in races and see if you can replicate it. If that doesn't sound doable, then just really focus on getting the right kind and amount of hydration in your next race.