Who taught you how to ride a bike?
It's less a matter of learning and more a matter of when I first got the hang of it. My parents both taught me in the usual way. My red-white-and-blue bike, bought when I was 4, came from Sears. It ran out of oil and sounded like a complaining cello, making the thing harder to ride than anything in a hefty spinning class.
The day I finally could do it without training wheels, though, must have been Easter when I was 5 (that would've been 1977). I only know this because the Wizard of Oz was on TV, which they played annually on Easter. After watching it, one of my parents (I forget who) ran alongside me and then let go. Off I went. I recall even riding around my St. Paul block.