Why not go try it out and see if it fits? I'm 5'9ish and ride a 53 for the most part, so a 54 might fit you. But you could have short legs and a long torso or vice versa. Take your measurements, look at a geo chart for each and compare where your current bike isn't fitting you, to the IRO's geo. But you could try making the All City fit you better first with a shorter stem and things like that. But if you don't want to measure yourself just go ride it and adjust it if needed.