This section of the Colorado Trail begins with a heinous climb up the Mount Princeton 4x4 road before returning to singletrack running along the flanks of the massive Mount Princeton. This section of the trail is generally rolling, with some climbs thrown in and some fast, flowy, beautiful singletrack sections!
The descent off of Mount Princeton down into Cottonwood is fast, loose, rocky, and raucous! Hold on for an awesome time, but be sure to make all the turns!
Once down in the Cottonwood valley/gulch, the singletrack climbs once more, steeply in spots and gradually in others, for a few miles as it makes its way up to the Avalanche Trailhead. This section of singletrack is not nearly as well traveled as the one going across Mount Princeton, but despite being a bit overgrown it's still easy to follow.
Once at the Avalanche Trailhead, there's only a half-mile or so of bike-legal singletrack until you reach the Collegiate Peaks Wilderness boundary.