Originally Posted by
Juan Foote
Even back when riding very regularly, doing 60+ miles a day a few times a week (or more) there was a point I would reach EVERY TIME right around 80 miles where cramps would set in, and I just never was able to stave them off. I believed a great deal that my own issue related to poor discipline about stopping to eat and intake fluids and salts early in my rides. At the very top form of my riding the absolute farthest I was ever able to ride was ~93 miles and even AT that was helped significantly by a couple of other riders in the club encouragement and cheering me on. By the time I got back to the car I absolutely could not move one leg anymore and had to be helped off the bike. In a way, that ride was never official because I neglected to get back to the starting point which was actually inside the racetrack a few hundred (more) yards away. My previous best had only been a few miles shorter than that before having to retire to the SAG wagon. My biggest issue related to my glute on one side. Other issue would be having that crazy arch cramp late in the night on hard days, particularly in the heat.
This is probably due to carb shortage, as you sort of surmise. What works best is to keep them coming, not eat every once in a while. Try a steady intake of about 30g-60g an hour, depending on how much power you are putting out, eating or drinking some carbs at least every half hour. Try that. A very simple thing is to eat 1/4 of a Clif bar every 15'. IME the first 3 hours of a ride is where you set the food and hydration routine that you'll use for the whole ride. If I get that right, I have a great ride. That's maybe the hardest part because in those early hours you feel so good.
There are essentially two sources of cramping: riding harder than you are used to, and shortage of fuel. As in the OP, neither dehydration nor electrolyte shortage are cramping issues.