Originally Posted by
tangerineowl
5' 9.5"/34" here. My experience was exactly the same when I first went through the bike shop sales thing. Everyone said 54-56; they just looked at your height.
My ideal is a 360mm reach; generally found in a 52.
There is no such thing as ideal Reach - Reach is dependant on Stack. Your ideal reach with 1cm more Stack than what ever you're talking about would be 357mm, for instance.
The range of stem lengths is designed to make up for minor reach differences. The difference in real top tube length between a 52 and 54 is less than the difference between a 100 and 110mm stem - around 1cm or less. The potential problem with going small for frame size is that it can make the front end particularly low, but some bikes with tall head tubes can more than make up for that, and are a good solution for those with long inseams for their heights.