Greg Lemond retired from the world of cycling four years ago, but his bike hasn't had a chance to get rusty. He spent two weeks last January riding from Hanoi to Ho Chi Min city on "The Vietnam Challege" organized by World Team Sports. The 12-hundred-mile ride was the first officially sanctioned event between the United States and Vietnam. It brought together veterans, many who were disabled, from both countries. Participants hoped to heal some of the wounds caused by the Vietnam war. Lemond went along to lend encouragement, help change flat tires and offer support. A new film, which will air on NBC Saturday afternoon, brings the 16-day adventure to life. Lemond says it was the most amazing ride of his life: