How To Select the Proper Road Bike Frame Size
Just because you are a certain height does not mean you should ride a certain frame size! There are a lot of variables when selecting the proper road bike frame size; however, the most important variable is going to be your reach. The reach is affected by the length of the top tube. Your reach can only be adjusted slightly by different stem lengths so there is generally only a few centimetres of adjustability, where as there is several inches of adjustability in the seat height or seat tube.
Interestingly, once you do figure out what frame size you are on a certain bike it does not mean that you are that frame size on another bike! Each bike manufacturer is different, for instance you could be a large (56cm) on most bikes; however, BMC fits large so it is likely you would be a medium (54cm).
You need to get on the different bikes and get a feel for them and see what is comfortable. Watch the video by GCN below: