Sounds like you are a man (touching my ball, *giggle*). Yeah, you are right, when you are standing with your bike shoes riding over the middle bar of your bike. You crotch should barely not touch it. Means that bike fits on you if you have 5"9, a 54cm frame bike should be fine. You can go one size down (51 cm) , but not one size up (58cm), which does not fit you comfortably!