Definitely not dehydration. You finished second and I assume it took you 2:45 or so. I calculate you drank 140 to 150 oz of fluid during the ride and at the end. You drank too much. I rode 132 miles that day and drank 122 oz. there is a limit to how much we can absorb. ....it varies from 16 to 25 oz per hour but can be more when cold and not exercising.