I'm 6'0" 180 lbs and I have a 58cm bike. I'm thinking 55cm is probably gonna be too small for you unless you have really short legs for a 6' person.

I see two statements, but no question, so I am not sure what help you need. I am your height and almost your weight, and ride a 57 to 59 cm bike. My torso is fairly short, and legs and arms long, relative to many others my height. My son is three inches taller than me, but his inseam measurement is the same as mine; his torso is where he gets his greater height. We are all different; best to go to a good bike shop for a professional fitting.

Welcome to the forum! :)

There was actually a post before mine that started the topic thread. The original poster had posted a link to a bike they were considering purchasing and it was a 55cm bike and they mentioned they were 6'0" tall. Weird that it's gone and it looks like my post is the thread starter.

I think I saw some other such posts scattered around BF, where it looks like somebody posted topics with similar titles, and deleted the opening post, leaving answers hanging, like bridges to nowhere. Ah, well. :)