Hi all,

I have been looking at some vintage "sport" touring bikes lately and have noticed something as I have poured over the fame geometry project. Note: I am asking this question specific to smaller frames 21" or 53cm. I make that point because in larger frames this change did not happen.

In the 70's it seems that head tube angles were 71 degrees for bikes in this size range. Somewhere in the early 80s the switch to 73 degree angles occurred. Trek seemed to do this pretty consistently. I should also point out that it seems the seat tube angles stayed the same at 73 no matter the size of the bike.

Can anyone explain why? What are the real world ride difference?