I'm 5'9", barely. I think there's a bump on the top of my skull that makes me that tall. so I would be on the very bottom end of the size of rider who would fit on a 55cm. I also can't reach my toes to safe my life, so I always end up on smaller frames and even with short stems so the bike it not too stretched out. with a 55cm frame, I don't think I'd feel comfortable with anything longer than a 80mm stem, so that would be a limiting factor.

hold up, let me be rational here. all this started because I want to put tires bigger than 35mm on a gravel bike and my current CX bike has that limit. when I am done, I will have spent over $1500 in order to go from 35mm tires (which actually measure to more like 38mm) to a bike that can fit 40 or 42mm tires. is this a worthwhile purchase for 5mm of extra tire space? Holy moley, I feel silly.