Originally Posted by
Carbonfiberboy
IMO setting setback by KOPS is somewhat random due to varying body proportions - what we're really trying to do is achieve balance between saddle and bars, little weight on the bars. I think KOPS works fairly well with 170mm cranks. That's a first approximation, then we move the saddle fore and aft to adjust for balance. Crank length doesn't really matter at all. What matters is one's fore and aft relationship to the bottom bracket, i.e. where one's foot is at the bottom of the stroke. That determines where one's butt is OOS and the general balance of the bike.
Hey, thanks for the comment. I thought you made some very good points in the other thread about the importancr of gearing in the whole system, so it's great to get your input here.
The model does not depend on KOPs, and I know KOPs is just received wisdom that is kind of arbitrary. The model has a built in variable for examining the relationship, but the model doesn't constrain this variable by default. it is a result of everything else by default. You could constrain this to vertical or a particular angle if you absolutely want a particular set up, though.
I have read that some argue that center of mass position is more critical, and it wouldn't be difficult to create a torso variable and hang a vertical line from the center of mass, if that is something that people are interested in.
I personally always like my knee behind and not over the pedal because I like to always have some component of my pedal force pushing me back off my hands. So I am not wedded to KOPs. I focus on knee-pedal above because, as I said, I was always convince that shortening cranks would destroy the knee offset I like, and I wanted to "test" this conviction. I was wrong, I'm happy to admit, because I forgot about the vertical component of the saddle height adjustment.