I'm not much of a mountain biker, but the past few Sunday's I've ventured into Henry Cowell Redwoods State Park in Santa Cruz County. The park's south entrance on Graham Hill Road is just 2½ miles from my front door, so I ride my bike there. The hiking trails are off-limits to mountain bikers, but bicycles are permitted on Pipeline Road, Rincon Fire Road, Ridge Fire Road, and Powder Mill Fire Road. Although these are called "roads," motor vehicle use is for authorized State Park vehicles only.
Powder Mill Fire Road is a short, wide dirt trail from Pipeline Road uphill to the park campground before ending at the Observation Deck. The observation deck is at the highest point in Henry Cowell and gives spectacular views down the San Lorenzo Valley into Santa Cruz and Monterey Bay.
Ridge Fire Road runs straight down from the observation deck to cross Pipeline Road. Ridge Fire Road between the high point and Pipeline is a steep downhill sand trap with monster water bars. I have difficulty negotiating this trail (i.e. it's not much fun either up or down) with my inexpert mountain bike skills. Beyond Pipeline Road, Ridge Fire Road continues as a nice, smooth dirt path with some leaf litter before it circles around to connect again with Pipeline Road.
Rincon Fire Road connects with Ridge Fire Road and winds steeply downhill to the San Lorenzo River. Most of this trail is somewhat bumpy dirt, though gravelly sections, steep turns and fallen trees across the trail add interest. Rincon Fire Road crosses the San Lorenzo River -- you must carry your bike and ford across the river -- where it continues steeply uphill to the park's southwest entrance on Highway 9.
While the scenery throughout Henry Cowell Redwoods State Park is spectacular, for mountain bikers the Rincon Fire Road provides the best views, with close up encounters with redwoods and stunning drop offs into the river valley. The Redwood Cathedral along Rincon Road is beautiful circular arrangement of giant old-growth redwood trees.
To return into Henry Cowell from the Rincon Road parking lot, you can bike up Highway 9 toward Felton to the visitor center entrance, where you can get back to Pipeline Road. To extend your ride, the U-Con trail runs across Santa Cruz's Pogonip park to connect Rincon Fire Road with UCSC Mountain Bike trails and the spectacular riding in Wilder Ranch State Park along the wild and rocky California coastline.