When I get in trouble on a longer ride it's all about my quads cramping if I try to stand. At least it has been to this point. Having experienced the bonk I know that is not what is happening to me. As I think this out and consider all the responses here I'm realizing that when this has occurred it seems to be as a result of the combination of a longer ride and significant climbing. This last ride included two climbs of steep grade and length. Both were at least a mile long. That may not seem so terrible to some but I am hovering around 190 lbs and that is 12 lbs over what I was when I got out of Basic Training in 1969 and what I consider my best weight to be. My theory has been that hauling that extra weight over significant climbing at age 67 is just wearing out my legs. Combined with a lack of proper fueling. I don't know if that's true but I do know I can ride the flats with any of my clubs B+ riders and some A riders and feel just fine. I also recover extremely well after climbs. But, climbing over time just leaves my legs burned out. And, I know I am not really good at staying of top of drinking in particular. somehow I just tend to forget to do it and when I do I feel bloated.