From SFBC:
Experience National Parks and the Bay Area Ridge Trail on a strenuous 12-mile loop that begins in the Presidio, spans the Golden Gate Bridge, and descends into the peaceful valley in the Marin Headlands. Lead by SF Bicycle Coalition member and Ranger James Osborne. For experienced riders with hybrid bikes;10 miles paved and 2 miles dirt trail. Reservations and information: 415-561-4323
