I just read the "throwup" thread and I am curious about this.
I drink between 1.5-2 liters per day and am not sure that is enough for me. I'm 175 6'2" and ride between 4-8 hours per week. I drink coffee, 2-3 cups (8oz) per day, and drink while riding (recovery periods: roughly every 10-20min). I DON'T drink suppliments while riding.
So, how much is too much, and is there a good way to objectivly measure sufficient hydration?