2nd 35 miler, no broken spokes and didnt bonk until mile 30.

Things are progressing nicely. Two gel packs and a banana. Next time bringing 2 gel packs and 2 banana's. Hottest day of the year, plenty of stops for water and I think next weeks ride will be a winner!!

And how did you get over it? I haven't done that many miles yet. The most I've done is 28 and we had three pretty long rest stops. I did 25 last Sunday and it was in the 90s. I think I may have "bonked" at around 22-23 miles but I had run out of water so I thought I was just thirsty. After we rested in the AC (we stopped and toured one of my husband's historic home remodels) and got some water, I was fine.

Anyway, good for you at making such progress!

Glycogen depletion. you run out of blood sugar, and then you fall over.
They say that your body "shifts over into a fat-based economy" when you run out of muscle and liver glycogen, but in my experience, running on fat barely gives you the strengh to stand in the porta-potty, and a brain that's mis-firing badly enough that you forget to pull down your shorts, too.

I've felt like I could hear blood boiling in my ears but I think that was from being too hot.

If you don't mind contributing further to my education, how do we burn fat when exercising if being in a "fat based economy" causes low energy/bonking? Thanks!

i find that i start getting charlie horses in my bad hand first, then the quads and hams follow.

When I really start to bonk, I get very confused, and feel like I am going to pass out. I can come back from it if I get some carbs on board, some sodium, and rest for a while. But from that point on, I know that I will pay for it later, as the cramps usually return when I am trying to sleep that night.

I used to use that fat burning thing a lot when I was doing martial arts, because I burned so hard so fast I always ran out of glycogen.

"Bonking" is when your muscles run out of stored glycogen. You can delay it if you keep simple carbs coming.

Also important if you're doing distance riding is not to push the "lactic threshold", a condition that exists when your muscles create more lactic acid than they can get rid of. That means taking your heart rate down a notch (i.e., riding a bit slower).

Recent research points to the importance of eating carbs after exercise. If you keep carbs in your stomach for up to five hours after your ride, you'll replenish your muscle's glycogen much faster, and you'll be ready to rock next time.

onedit: also critical, especially in heat, is water. More than you think you need.