Chuck, Your explanation makes sense. In my case I am riding Brooks saddles and would need a size bigger frame to use those short posts. Think I'll pass on that experiment. Though I was offered an approx 26" Stella not long ago! The seat tube angle being slack vs steep is easy enough to see. The bottom bracket height I have a bit harder time seeing. Is there a particulat time span when manufacturers were changing the bottom bracket height(and seat tube angle and length)? Seems like most road bikes sold today, and the last 15 - 20 years, are more "crit" geometry than anything else.
Pete Geurds Douglassville, PA
In a message dated 12/18/2001 2:18:08 AM Eastern Standard Time, chuckschmidt@earthlink.net writes:
> Here's my explanation:
>
> The Campagnolo 130mm micro-adjust Record seat post came out in 1956
> before the advent of plastic saddles. Leather saddles like the Brooks
> B.17 have very tall frames measuring 70mm from the rails to the top of
> the saddle in the middle. Plastic saddles (intro'd around 1960)
> typically measure 45mm or so from the rails to top of the saddle.
>
> If you add 130mm for the short seatpost to the 70mm for the leather
> saddle you get a total of 200mm. If you add 180mm for the long seatpost
> to the 45mm for the plastic saddle you get a total of 225mm, only 25mm
> (roughly one inch) taller.
>
> One reason the frame you rode in 1950 measured larger than the frame you
> rode in 1985 (before the current mt. bike seat post craze) would be the
> low bottom bracket and slack seat tube angle that would increase the
> seat tube dimension. The stand-over height of the top tube would be the
> same for the 1950 bike and the 1985 bike, but the BB would be closer to
> the ground, hence the "larger" 1950 frame.