Cultus Mountain and Lake Loop Trail is a 11.9 mile moderately trafficked loop trail located near Bend, OR that features a lake and is rated as moderate. The trail offers a number of activity options and is accessible from July until October.
I hiked about one half the 'trail', and ran the other half. After doing so, I agree 100% with the trail's classification as a bicycling route. From Cultus Lake Lodge, approximately 1 mile consists of paved road, and another 3 miles of relatively high-volume gravel road puts you right at Little Cultus Lake. Once you get through that, you're left with about 1 mile of rough, old Forest Service road to Deer Lake, and then about 8 miles of nice, shaded single track roughly paralleling the lake.
A better choice for runners and hikers (of similar length) would be to head from Cultus Lake Lodge north and then west along the northern bank, all the way to a nice gravel beach at the western edge of the lake, then back the same way. If you're looking for more of a challenge, throw in another couple miles to the top of Cultus Mountain.
The two-star rating is from a hiking/running perspective, but I think even from a cycling perspective, the traffic volume on the roads, and several miles of gravel washboard on the actual loop, wouldn't allow for a rating above 3 stars. Beautiful area though--just need to get some more of the numerous trails on the map.