Originally Posted by
Campag4life
Saddle width is often equated to the distance between ischial tuberosities or what are generically referred to as sit bones. This is an inaccurate oversimplification however. The pelvis as it rotates forward in terms of saddle contact narrows dramatically. So choice of saddle is probably more of a function of your pelvis rotation or lack thereof than any genetic distance between your ischial tuberosities or so called sit bones.
So sitting armchair fashion on an Ass-O-meter isn't going to tell you what your best saddle width is going to be for riding.
I would say that you are setting up a false opposition here. Choice of saddle should be informed BOTH by pelvic rotation and the distance between the sitz bones. If one was to oppose them, knowing pelvic rotation and not sitz bone distance is more useless than knowing sitz bone distance but not pelvic rotation. Ass-o-meters do what they are supposed to do, but it is a case of garbage in - garbage out. Why, for f's sake, would one sit armchair fashion on an ass-0-meter? You are right, it is a quick way to get a meaningless number, but that is not the fault of the ass-o-meter.
If it is going to be a meaningful exercise, one needs to adopt a position similar to the one on the bike when sitting on the ass-o-meter, for the reasons you have outlined. This does not mean discarding ass-o-meters, it means using ass-o-meters properly and interpreting the information correctly.