When you're in the mood for some mellow riding at a moderately high elevation, this makes a good quick option from Boulder. It's a lot of dirt road riding, and some pavement, but the scenery is nice and the grades are never steep.
I like to start this ride from where Sugarloaf Mountain Rd climbs up from Sugarloaf Rd, which breaks the main climb in half - some at the beginning and some at the end of the ride. There's plenty of parking near some mailboxes at the intersection.
Climb up Sugarloaf Mountain Rd. until you get to the very large parking area and trailhead. If you have time (and a bike lock), it is WELL worth hiking 0.8 miles up to the top of Sugarloaf Mountain for one fo the best views in all of Boulder County.
The Switzerland Trail
comes through this trailhead, so you could go two ways. For this ride, choose the more southern option and cruise along for 5.6 miles of easy, mostly smooth dirt road. This was once a rail grade, so the angle is gentle and the miles go by fast. There are a few great views along the way.
This ends at the Peak to Peak highway (72), where you'll turn south (left) and go about 1 mile to the Gordon Gulch trailhead. The highway is downhill here and it's easy to speed past, so keep an eye out on the left side of the road.
Use the MTB Project mobile app for the next section or you'll most likely get lost!
You'll now be following the Gordon Gulch Trail
. Look for signs for FR 226 and FR 233. When in doubt, follow 233 or use the mobile app. It's extremely confusing in here. Many side roads go up and down very steeply but if you stay on the correct one (generally taking left turns) it's relatively flat.
Follow this web of roads for about 2 miles until you arrive at a singletrack that follows a creek down the valley. There are trails on both sides of the creek, but you want the much more obvious one on the west side of the creek that's marked 233.
Follow this singletrack on easy ground for a quarter mile, than navigate a steep section of rocks about 100 yards long. Some people may walk this section.
Then there's more easy singletrack for a bit over a mile down a really fun descent through nice forest and meadow.
You'll end in a small neighborhood and follow Primos Rd, which leads down to Sugarloaf Rd. Climb back up the road to the start.