christian try to go explain why he took on the challenge. >> translator: we create contrast in our lives, so that for things to be really great, we must also experience hell. standing on that line is hell. it's damn good to come home and sit on the sofa and relax. >> be careful. oh. oh, no. a mountain biker plunges head over heels down a rocky cliff. >> it's a hard experience you think you see another human being in the process of dying. january 1st, 2004, chorizo gorge, southern california. for experienced cyclists, a new year's day trail ride has become an annual tradition. >> we try to do a big ride every new year's day to start the year off right. >> bill's helmet-mounted video