The way I came up the mountain today has 3 parts for a total of about 2.7 miles. The first mile is fairly shallow, then you give up a little elevation and hit the middle steepest section. I'm guessing 20+% but don't have a gps reading or anything. Steeper than anything in Texas, except the little stinger Steve, Bud and I climbed on the Two Tickets to Paradise Perm.
Here is a bikely link for the climb portion I'm refering too.
http://www.bikely.com/maps/bike-path/Shades-Mountain-Climb-up-CR1 looking at the elevation profile will give you an idea, but I know for a fact that there are no flat spots on that section despite the graph.
Take Care,
Nelson.