>> how the amount of seatpost is affected by the seat tube angle going from 71.5 degrees like on my Hillborne to something with a more "aggressive" STA like 73.5.
Short version, it isn't. The simplifying assumption is that we don't change the fore-and-aft position of the saddle as we change the seat tube angle. To visualize, imagine you're getting on the bike to set the initial seat height. The classic method that always gets me close is to fully extend my leg and put the heel on the pedal in the downward position. Then seatpost-seattube-crank form a straight line, and the geometry does not change when the STA changes. On the other hand, if you imagine a frame with adjustable STA -- ridiculous, but this is our gedankenexperiment, so we get to do whatever -- then there is a slight lengthening of the exposed seatpost as the STA decreases and the saddle slides forward on its rails to stay in the same place relative to the handlebars and bottom bracket. As always, you have to fit your body to the entire bike, there's no way to change only one variable. On Wednesday, September 24, 2025 at 11:42:03 AM UTC-4 Davey Two Shoes wrote: > Hey Gang, > I can't get a grip on this. I am what we call "seat post challenged" In > that I have a very short PBH resulting in less than expected exposed > seatpost per size per my height. Hope that makes sense. > > So I'm wondering how the amount of seatpost is affected by the seat tube > angle going from 71.5 degrees like on my Hillborne to something with a more > "aggressive" STA like 73.5. If we assumed the seat tube length were to > remain the same length and be measured the same, would I gain or lose > exposed seat post? > > Sorry to be wordy, I have trouble explaining what I don't understand! > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/0de508e8-b0ed-42ba-8472-c6dcc03dea1dn%40googlegroups.com.
