We hike this loop at least once a month, going up what's marked as Queenstone Rd up to the Fire Road, over to Big Rock Ridge and then down the trail which we've dubbed "Goat Trai" since you'd need to be a billygoat to come UP that way. It's a great workout and some very nice scenery especially on the way down as the road winds around the crevasse back down to the stables off Rubicon.
A beautiful, steep climb up a natural steep canyon. We only had an hour, and after an hour and a half, we were still climbing, hoping to get to the fire road. We think we were close, but turned back and went down the same way we came. We hiked up and down in about two hours. Count on 3 full hours to do the whole loop. It's a beautiful, natural environment, with great views, and much shade along the way.