The bike ride UP Mt Evans is a real kicker. Nothing like seeing spots to remind you of the altitude.
That one is probably beyond me, although I've seen an amazing number of folks doing it - and just about every other grade there is to be found in Colorado. I recall driving Timber Ridge Road once and seeing more bikes than cars over about a five mile stretch - at the 11K level. The state has got to be the most biked per capita in the nation. I swear, there are more bikes than autos on the Boulder roads in the summer, as well as a really high percentage of trails in the area that allow bikes.
Just thinking about Colorado gets me jonesing for another trip out there. Rocky Mountain NP is one of my favorites, and I've been to just about every major NP in the lower 48. I celebrated my 50th birthday a couple of years ago by dragging my aching butt up Long's Peak, second only to Whitney on my personal "What Was I Thinking?" list of grueling dayhikes. Overnighters are more my speed now. I think I'm past the point physically of pedaling a bike up that kind of mountain. Breezing down, however, is another thing . . .