That trail is seriously tough in terms of cardio and patience. It is a lot of work but can be fantastic if the trail is in good shape. It is kind of a 50/50 proposition though. Sometimes its better just to do circuits of specific sections when the trail is tore back in places.
Best Difficult Bike Trail - 2012
Golden Eagle Mountain Biking Trail, Angeles National Forest
It could alternately be called the best or worst, depending on how many times you crash, but the 16 miles of single-track trail — cutting across oak-dotted hills and a dusty, manzanita-covered mountainside with views of Pyramid Lake, Quail Lake and the Antelope Valley — is breathtaking either way. The Golden Eagle Mountain Biking Trail in Angeles National Forest starts on the Old Ridge Route, rustic predecessor to the I-5 Grapevine, where, buried underneath the sage, is the foundation of the former Sandberg Summit Hotel, a ritzy rest stop for Model T Fords and Studebakers making the long, windy drive between Bakersfield and Los Angeles. Today, the remote trail and an adjacent fire road, marked with a bullet-riddled "No Thru Traffic" sign, usually are empty — which just means riders who make the trek have carpets of wildflowers (in spring) or curtains of fall colors (in autumn) all to themselves. Take I-5 to the 138 toward Lancaster and turn right at Old Ridge Route. The trailhead is about 3 miles up. —Tessa Stuart