What is the fastest average speed a Tour de France has been won with?

Explanation

The winners average speed of the Tour de France has continuously improved. The first tour was won with 25.67 km/h. The limit of 30 km/h was exceeded the first time in 1934. In 1956 the winning rider rode more than 35 km/h. Lance Armstrong was the first to break 40 km/h in 1999. In 2005 he increased the average speed record to 41.65 km/h which still stands today.