thanks for the advice, mihlbach. What did your son learn to ride on at age 4?

Regarding the safety, those are interesting points. I'm not that committed to getting him to ride a fixie, just am excited about him riding. You know how it is. I figured that it'd be good to learn on, and that he could make up his mind about subsequent bikes after he rides other kids'. Wouldn't most of what you say about pedal retention apply to coaster brakes, too? Though I see your point about the low gear ratio/hill thing. But for a first bike that rarely leaves the apartment complex or park (I wouldn't take him anywhere near the street, since we live on a massive boulevard in LA), he probably wouldnt be going down too many hills. Though Lazarescu seems to have made it.

but yeah, I can be convinced to bag the whole thing. Just an idea I'm kicking around.