It's true that the average age of a first-time Tour de France winner was 27 both prior to WWII and after, right up through Indurain's first victory. But, if we look a the multiple-tour winners starting with Bobet, it's 24 yrs old.
Bobet: 28
Anquetil: 23
Merckx: 24
Thévenet: 29
Hinault...