Tantalus Flats is a 24 mile point-to-point trail located near Boulder, UT. The trail is good for all skill levels and primarily used for mountain biking.
Did as a mountain bike trip in mid-june. While some guides recommend starting at the lookout, we saved 3 miles and parked just off the highway on the road to Bown's Reservoir. Fun downhill for quite some time with great views of the Park and Henry Mountains. We took the road and passed a biker later who had taken the ATV track. He said it was really bumpy (glad we didn't choose it). At some point you will see a sign saying Tantalus 5, take this left. As you lose elevation and get closer to the park, the road gets a lot more sandy patches. Great views all of the time. After crossing Tantalus Creek you will climb until you get into the park. Just after crossing into park there is a downhill section that can be pretty technical. I rode it but my wife walked her bike. Most of the ride is easy on the technical except for this part. Riding out South Draw to Pleasant Creek is really fun and flowy. We made it onto the scenic drive where our ride found us and saved the last 8 miles to Fruita. Was 101 degrees in the park, whew! A breeze kept it pretty cool for most of the trip.
Tantalus Flats is reached from Hwy 12 on FR 186 to Lower Browns Reservoir, then FR 168. Nothing was that bad when I traveled it in 2009. We continued on into Capitol Reef NP. There was a fairly tough spot just inside the park. You go over a ridge, and the road goes right beside a deep washout until you get off the ridge. Several miles farther on, you cross Pleasant Creek, and you are on the Scenic Drive back to Fruita.