MinnMan

I had my first and only serious bonk on a ride in Spain this past August. For me, it was a combination of factors, and I don't think there is particular culprit to the OP's bonk or mine. Sometimes there is a brew of challenges that produces a tough result.

In my case, I bonked on the last climb of a ride that was about 80 miles long and had maybe 7000' of climbing. the last climb was about 1200' or so and about 6-8% for most of the way.

It was not my fitness - I have ridden centuries nearly every Saturday all summer, and I've done harder rides before, including one earlier this year that was a similar distance but with ~9000' of climbing. It may have been my nutrition or hydration. I ate too little in the morning and didn't keep up during the ride. I probably also didn't drink enough. And it may have been the heat -though it was cool when I started out, by the time all this happened it was mid-afternoon and maybe 95 °F.

One interesting thing is that i knew the bonk was coming, but failed at prevention. I began to bonk in the dozen or so miles before the last climb,, and I stopped and ate a bunch of trail mix and bought a coke at a local cafe. I also drank plenty of additional water. But I was already so deep-in that the additional hydration and nutrition were too late. I wonder if anybody else has experienced this?

I got about 300' of climbing in that last climb and I simply could not continue. I have never previously stopped on this kind of climb. (A couple of times doing climbs of >3000', I have deliberately stopped midway through to take a break.) I was so exhausted, I could barely get my leg over the bike. After a time, I began to walk up the hill, but even that was too much. I had to stop every few hundred feet because the walking was too much effort. It was TOTAL exhaustion. Getting over that last hill (90% walking) was misery.

I had planned to ride the next day, but I needed to give my body a rest. The following day I did a much flatter (3000' total, I think) 90 mile ride (I was in Girona after all, I wasn't going to sit in town and not ride!) and I was OK, though I did it very slowly and was more tired at the end than I usually would have been. It took nearly a week before I regained my full strength.

It was an interesting experience. I don't recommend it.