I did a week long ride across part of Colorado. I rode three days of the TA trail, starting with the Hoosier Pass. From the west, the route takes you up Colorado Highway 9 to over 11,000 feet. There are not a lot of paved shoulders on the road up there. There's also not a lot of oxygen up there...My rig was 70 pounds, bike and baggage. My smallest gear was 26/34. I was ok for most of it until the switchbacks towards the top. I was going so slow I didn't feel safe, so I mostly walked those. Most of the climb was 7% grades or less until I hit the switchbacks, so of the 11 mile ascent out of Breckenridge, I probably walked 3/4 of a mile or so. I think if the 12% grades would have been at a lower altitude, I would have been fine.
The second day I rode to Canon City. There are a couple of 9000 foot hills there, but it's a gorgeous ride. If you have any energy left when you hit Canon City, take Skyline Drive as you enter the city...It is an amazing road and worth the climb. The third day to Pueblo is very nice and significantly less altitude.