Originally Posted by
Frkl
I know we all know this, but the CPSC obsession with crotch-clearance and stand over height is just that, an obsession brought about by the need for some sort of simple, consumer-understandable, manufacturer-compliable number for a "correct" bike fit. The cascade effect was that bike manufacturers didn't want to get sued by consumers or fined by the government for frames that were "too big," so the made-up standard became a "rule." Of course in reality, anyone who has crashed knows you don't land two-feet-flat-on-the-ground, straddling the top tube over a bike with both wheels on the ground, and people who ride longer distances just don't put their feet down . . . . well, it is a legal reality but not an actual cycling reality. the rule has probably caused a lot of pain for riders--hands, back, elsewhere.
But for the average consumer, some sort of easy rule was necessary. I guess the shame is that the rule became reality.
Stand over isn't a rule. But it does mean that if a bike maker wants bikes to both fit and provide standover clearance, they aren't going to make 57cm frame with a 51cm top tube. There is no reason to have the ratio of seat tube to top tube out of whack, unless you have unusual fit needs. And factory geometry isn't for those people.
Now we have sloping top tubes and tall head tubes so even the long and short legged people can stand over fine without getting a custom frame.