Originally Posted by
PepeM
Do people really 'run out of fuel' in rides of less than two hours? Get tired, sure, but run out of glycogen?
Probably not, but possibly for someone with hypoglycemia issues or no history of workouts longer than that.
I tossed it out as the first and simplest possibility among others because it's the easiest to test for. No trip to the doctor or exercise physiologist. If eating during the ride solves the problem, the OP has a usable answer even if not necessarily knowing the true cause or mechanism.
OTOH- if carrying food doesn't solve it, the OP can move on to other possibilities.
In any case, with repetition and gradual working through this wall, odds are the OP will adapt and push the wall out farther.