Originally Posted by merlinextraligh
Back in the day, people used to talk about bike sizes by their wheel size. So a kid might start out with a 20" , move to a 24". Then an adult one speed bike would typically be a 26" Then "10 speeds" and "english Racers" were 27". Of course it doesn't make much sense to talk about a bike by wheel size, but that was common circa 1970's bike boom.
That's still how you size kids bikes. Even all the "high-end" 16" and 20" Specialized Hotrocks we have hanging around the garage are spec'd with wheel sizes (actually outside diameter of the tire).
This is common for bikes with only one frame size. Hotrocks come in one frame size for each wheel size.