When I was a kid, I was adventurous to a fault. I was legendary for the bike wrecks I used to get into.
When I was about 10 or so, my friend Ray and I were biking around the hills of El Cerrito, along with my older brother Mark and Ray's brother Sertha. Actually, I was on the back of Ray's bike, since my bike was in bad repair (presumably from the previous week's spectacular crash) and goading Ray to take more risks and live a little. His bike's brakes were out, so we had to hop off and walk the bike down the steeper hills.
A time came when we were at the top of a long, steep, curvy street that ended in a "T" intersection. I was sick of walking down hills when we seemed to have two perfectly good wheels to go down a whole lot quicker, and the lack of any means to stop seemed like an awfully abstract problem. Ray, knowing what was coming, immediately said, "No Matt. You've made me do some crazy stuff, but this is too much. My mom will kill me if I get killed because of you. I'm not even supposed to be playin' with you, man..."
15 minutes of teasing, goading, and calling him "chicken" later, he agreed to go down the hill. The plan was, he'd control our speed by putting his sneaker on the front tire as a sort of provisional brake, so we would not get going too fast.
About 15 seconds into our journey, we were going, oh, 35 or 40 miles per hour, and his sneaker was decidedly not up to the task of stopping 130 pounds of kids and their bike. That's when Ray started screaming.
About two thirds of the way to the bottom of the hill, Ray raised himself slightly from the seat, and put his foot down on the front tire with all his might.
His foot rode up the back of the tire, and directly into the front forks where it lodged firmly, which stopped the front tire. Instantly. At 40 miles an hour. The bike instantly "endo'ed" and cartwheeled into a parked car, Ray attached. I was launched into the air over the car that Ray was messily impacting, and remember thinking with startling lucidity, "When I land, this is really, really going to hurt..." - just before I landed in some lady's rose bushes. Ray didn't break anything, and made me give him my tee shirt to absorb the blood from his cut face, and I also had to carry the two halves of his bike home. When I got home, mom said I looked like I'd gone ashore at Normandy on D-Day.