Originally Posted by
Mosman
With such calculation it puts my on 54 more likely a medium in giants sizing
A ballpark figure. I can't emphasize enough that you try them out. That formula was from Greg LeMond's book back in the mid-80's. That was before sloping TTs.
I don't know if it's been mentioned but you can ride a range of sizes. They are typically know as Race, Eddie and French fits. I can ride 54 to 58 frames but "square" 55 is perfect for me.
Back in the day, racers would use the smallest frame that fit because it was lighter.