October 25, 2014
This is positively vicious as an out and back. It climbs 3,100 verts in just 6.8 miles and most of the first two miles is pretty flat, so the rest is positively heinous. And there are long, highly technical stretches which would be tough on level ground, let alone on a 12% (or more) grade. I recommend doing this as a shuttle, starting at the same point as the Winsor Trail and then forking onto Rio en Medio shortly thereafter. Even then, you'll probably dismount a few times. The canyon is positively gorgeous with ponderosas, aspens, and lots of waterfalls along the way. There are also a lot of creek crossings. Expect to get your feet wet, especially in spring.
Overall, this is a great trail for a confident, adventurous rider.