Who are those boys in the photo? Cliff Christl
The above picture is proof that the bike tradition, one of the Packers' oldest and most uplifting, dates to at least the first year training camp was held at St. Norbert College and practices were conducted across the street from what is now Lambeau Field.
This 1958 photo is the oldest that I've found of Packers riding bikes from their locker room outside of what was then 2-year-old Green Bay City Stadium, through the east parking lot to the practice field along Oneida Street, just a short distance away.