20 or so years ago, I lived and worked in Denver, Colorado Springs, and also did a job in Beaver Creek. Lots of great mt biking all over. Stop in one of the many bike shops, and purchase a trail book. It will show you many trail heads and loop routes. When I was in Denver, I particularly liked biking around Red Rocks. It’s a place that shouldn’t be missed. When riding in Co, be prepared to be winded a lot, especially when riding technical single track stuff. The air is pretty thin up there.
Agree with the local bike shops. While I well remember some very special places along the Colorado Rockies, all of them are from over 20 years ago so I know not what may have changed.
However, if you are going to venture to the Grand Junction/Fruita area Tim... Go South Young Man.... to the Ouray to Silverton (to Durango) areas of southwestern CO. Ouray is around 7800' (a very fun and beautiful place), Silverton is around 9300' and the San Juan Mountains in that area are up to well over 14,000'. An easy 'loop'
through some beautiful country past a lot of high mountain lakes/creeks would be Lime Creek Road. Starts at about 9500' by Casacade Creek a couple of miles up the road north of Purgatory Ski, and comes back into the Million Dollar Hwy some miles north by Deer Creek. An almost all uphill Silverton to Cinnamon Pass (approx 12,600') ride should be doable for an easterner, with a somewhat challenging back down (one side of the two track is straight down from 0' at the bottom to about 2000' as you get closer to the pass). A more challenging ride would be from the Million Dollar Hwy up over Black Bear Pass to Telluride. It is a serious 4X4 road to give you an idea of the lay of the land.
Speaking of long ago and Beaver Creek... in the late 80's I spent some time along the upper Beaver Creek drainage studying and logging the life history and larval food plant associations of
three species of
Hemileucinae, testing and proving a pheromone theory between the
three species (
Hemileuca hera hera;
H. elglanterina annulata;
H. nuttalli).
(Among similar others, I was a serious Lepidopterist for over 50 years, and this subfamily of
Saturniidae was among my special interest families of worldwide Rhopalocera and Macro Lepidoptera.)