Originally Posted by
miyata man
I have a geeky bike related math question.
How does one go about determining the variation at a set distance in half degrees? This is in regards to seat tube angles from the center of BB to top of saddle. In this case 72.5-73.5 ST with a saddle height of 77.5 cm.
My road position requires a straight post on a 73.5 degree ST that puts the saddle rails nearly centered. The frame I'm looking at allows replicating it exactly bar a shallower ST angle messing things up. My guess is the answer here falls beyond the scope of saddle rail adjustment from centered.
Thanks to anyone with the basic math skills to solve this.
Not totally clear to me what you're asking, but if the BB to saddle height, measured along the 73.5 degree seat tube, is 77.5 cm, then every degree change in the seat tube angle will require moving the saddle fore-aft about 4 mm in order to keep the saddle in the same place relative to the BB.