Originally Posted by
noglider
Who says the B17 is for upright riding? I don't remember seeing it on an upright bike, but I'm sure there are some with B17's. I have B17's on most of my bikes, and they have drop bars. I'm one of those who prefer the nose tilted up. Mine is tilted up more than most people's, so there might be an anatomical reason. Maybe my pubic bone is higher in relation to my sit bones than on other people. I haven't measured that in myself or in anyone else.
My theory is: the outer side edges of a B17 are sloped forward-down more than the center section of the saddle, so the wider your sit-bone contact points the more saddle up angle on you need. Sit-bone contact width is a combination of bone structure and forward lean angle - more aggressive riding stance narrows the width of the contact points.