Originally Posted by
Campag4life
not sure what you mean by false opposition. Did you mean false premise or supposition?
Good point about how to sit on an Ass-O-meter. Btw, have you done this? When sitting in a forward rotated position on a Ass-O-meter do you really get 2 distinct points? I would like some proof of that. Seems to me the inferior ramus where one really sits on a road bike saddle is in effect, two converging boney rails or protrusions. I am quite sure they would not leave a clear demarcation of sit bone spacing when sitting in a proper pelvis forward rotated position.
Therein leads to the further myth about correlating an Ass-O-meter measurement to actual saddle width. How much side to side distance should one leave to each respective edge of the saddle to each touch down of the pelvis to the saddle. 5mm? 10mm? This isn't quantifiable with any sort of science.
False opposition - you took two elements of a fit, then put together an argument as to which part is better. It is a false opposition, because it is not "either/or", it is "and". You need to account for pelvic rotation AND sitz bone distance. Either parameter is less meaningful without the other, but your initial post makes it sound like we should choose one over the other. So it sets up a false opposition - these two parameters are not contradictory, both should be elements of fitting a saddle.
And yes, this is exactly how I used an ass-o-meter, and yes, there are definitely two distinct points. In terms of the physiology of how the pelvis interacts with the saddle, scroll down near the bottom of this, there are even fun pictures:
http://www.cervelo.com/en/engineerin...-saddles-.html