I think of it this way...if you were taking part in a bicycle race and could only have one set of brakes for some reason, would you put them on the front or rear wheel?
Well, on the back, of course...you know that you're going to flip over if you're riding fast, brake the front wheel, and that rear end has to come swinging around somehow.
When I was a kid, we had an ancient scooter called a Puky that my dad had dug up somewhere. The thing had wide, inflatable tires and would roll forever with one good kick. You could also sort of sit on the back fender while riding it, although that was dangerous as heck. Anyway, the Puky had a really crude front brake that was basically a metal pad that pressed on the front tire itself, but nothing in the back. It did not us kids long to figure out that you were in for a world of hurt if you hit that brake with any kind of speed going.
My dad was so funny...when he was done with something, he felt that thing should not be used anymore. When I got too big for the Puky, my dad put it out by our trash at the alley just before the garbage truck came. Two kids found it immediately and started riding it...dad was livid, screaming and swearing by our kitchen window. I told him it was great that it was going to be used, and he kept raving about kids leaving his garbage alone. He bought all kinds of things used (Salvation Army was my toy store as a kid), but he would never donate anything or let people have his old stuff.
Dad bought a used full sized ping pong table that I had tons of fun with in our basement as a kid...when I moved out, he took an axe to the thing. He claimed he couldn't fit it up the stairs, but he had gotten it down there...I could have helped him push it up during a visit if it was too heavy for him. He just didn't want anybody using it after him.
