I'm working on building a nice little motor suitable for Last Chance or Colorado High Country in a few years. I've got a ways to go, but I'm able to do 80+ miles without dying or even being sore the next day, particularly if I remember to pace myself. I expect to complete a double metric by the end of the year (hoping for a dry winter, or at least that my cycling gear does what Pearl Izumi says it will).
Right now I typically aim for 105-115 rpm on my rides, although I played with a target of 120 for 40 miles on Sunday. I really pushed my pace on that ride, and though I was pretty wrecked when I got back, I managed to sustain 18mph into a 10+ mph headwind for the return 20; I was happy with that. When I set out I paid particular attention to circular pedaling and at one point screwed around with 140+rpm for a few hundred yards (without bouncing out of my saddle).
I've read that higher cadences (90+) use fast-twitch fibers preferentially, thus consuming glucose from the bloodstream which can be replaced by a sports drink (or so says John Forester, IIRC). Lower cadences are supposed to recruit slow-twitch muscles preferentially, which draw on fat stores for their fuel. It seems like endurance riders ought to prefer the slower cadences, because it's damn hard to replace 6,000+ calories day after day, all while on the bike. In your experience(s), is this true?
I know this borders on the optimum cadence question, which has been beaten to death elsewhere. I just want to know what you guys and gals do on the longer events. How fast do you spin?