Back to the Horsetooth Mountain Ride map.
From the top of the initial service road you can take the West Ridge all the way past Horsetooth Rock itself and on to the radio tower service road. This trail is up and down. I find the pitches to be a bit too dramatic (steep) to be enjoyable. I've tried riding it from the radio towers back towards the initial service road, and in the opposite direction. I can't ride continuously without having to stop and push/carry my bike, so it isn't too fun for me. There are some good rideable sections in there, but too much "bike-hiking" for my tastes.