I was going to start a related thread - but I had a similar situation last night. I ate as I normally do prior to an evening ride - I had a roasted chicken wrap at home. My Camelbak had Heed/ice in it (I have a smaller one that I reserve for this purpose).

Energy wise I felt fine, but as the OP said, I felt "urpy" for the first 9.5 or so of my 15 mile ride. I was riding in a fairly shaded park and wasn't pushing things overly hard. After 9 miles I almost went home - the large nature park I ride in during the week is across from my apartment - but decided to take one more lap and my stomach finally settled down.

In the end my time was better than usual even though I had tried to take it easy - avg spd. was a PB of 14.7. I do seem to remember having the same symptoms last summer on very hot days - though it wasn't THIS hot.

So for those who ride after dinner on weather like this - do you change your usual pre-ride dinner for lighter fare? I hydrated all day yesterday, as well as before and after my ride. I felt fine afterwards.