WheelNut wrote: ↑
Fri Dec 06, 2019 7:42 pm
moock wrote: ↑
Fri Nov 08, 2019 1:42 pm
Only three numbers matter when it comes to bike FIT!.
-Head tube angle. The difference between 73 and 73.5 degree is massive when using a stem longer than 100mm.
So, what you're saying is a frame with a 72* seat tube angle will fit the same as a bike with a 74* seat tube angle. Reach doesn't factor into road bike fit. Bar to saddle, saddle height from BB, saddle setback from BB, and bar to saddle drop are really the relevant dimensions to assess a bike fit. Of course the industry doesn't build their geo charts this way because they arem't focused on fitting humans, rather they are focused on building frames and (maybe) describing bike handling. Anyway, it is possible to get all these dimensions from a standard geo chart, but it isn't as easy.
I'm confused where you're going with this. Reach and Stack are key. Seat tube angle is pretty insignificant given that you can adjust the position of the saddle given long enough rails, or changing out the seatpost for something with a different offset (as Nefarious said). A lower seat tube angle may affect your for-aft CG, but so will chainstay length. Headtube angle is significant more for handling than fit in my oppinion as the for-aft difference in a couple of degrees given the same length stem is minimal. Height can be adapted to by using a different angle stem or adding/removing spacers. Steeper HT affects trail, and the performance differences can be offset by changing the rake, but that's a bit more complex of a task and we're talking about fit here.
Bar to saddle = REACH + stem length + saddle setback from BB
saddle height from BB: adjustable with seatpost
saddle setback from BB: adjustable with seatpost/saddle rails
and bar to saddle drop: STACK +/- spacers +/- stem rise (º)
I was able to exactly replicate the position of my 56 Sprint on my 54 Cervelo Aspero and nearly able to replicate it on my 56 Trek Crockett, all by varying saddle height/setback and the stem and spacer choice. Three very different bikes, almost identical position. The only reason I couldn't replicate it on my Crockett was because the stack was too high, I would have needed something like a -20~something degree stem and only had -16º. Didn't want that low of a position on a CX bike anyay.