Cycling from Estes Park to Loveland is an interesting and scenic trip that is mostly downhill or flat. While it is of course possible to go directly on the highway from Estes to Loveland, I prefer to go via Glen Haven.
Starting from the Safeway in Estes, go to the right up the hill past the Stanley Hotel and turn right at the next street, Devil's Gulch Road. This road leads to the McGraw Ranch (a beautiful valley worth a stop to look, if not a detour) at the base of the Twin Owls, then turns right and follows Lumpy Ridge eastbound. After the end of Lumpy Ridge, the road turns left and descends steeply via switchbacks into the valley; this descent is so steep that I worry about rims overheating from brake friction. Once down the steep part, you enter the village of Glen Haven.
Glen Haven is a picturesque hamlet with a few stores and restaurants and a post office, as well as a nice stream and some picnic sites. The road continues down the stream through rural country, finally meeting the main highway at the small town of Drake. There isn't much traffic on this pleasant section of road.
Below Drake the traffic is fast and heavy; however, the road has been widened, and a marked-off shoulder forms a good de facto bike lane. The road follows down the Big Thompson canyon, the site of a dramatic flood about two decades ago. The end of the canyon is the spectacular Narrows, with near-vertical cliffs on both sides and a steeper descent. Here the road narrows too, so use caution. Because of the steep descent, a bike can nearly keep up with car traffic, though there usually seems to be a speed demon who feels compelled to pass. The Narrows is a fairly short section.
Following the narrows is the Dam Store ("best store by a dam site") and the road levels out, rising to cross a hog-back ridge. Here the traffic is fast and unfriendly, so use caution. Within a few miles you are in Loveland. The road goes past the lake, a nice place for a stroll and a good place to meet your ride back to Estes. Elapsed time for the trip down was 3 hours 45 minutes.
Rocky Mountain National Park: The High Peaks