Wow, I'm 71 and my height hasn't yet changed. Or less than 1/4", still at 73.25"

60 X 58cm has always been my size. When I wanted to ride the classic vintage euro bikes, my patience required I accept a range of sizes to obtain the bikes I wanted. So, my group runs from 58cm - 62 seat tubes. The 58cm bikes will be the first to go.

So I guess I would size up - but top tube length, stem length, seatpost set back, handlebar dimensions, and the specific saddle all play into making the fit a perfect dream. Or not.

the big problem with most modern bikes that come in 4 or 5 sizes, the jumps between them are bigger than in the past.