Originally Posted by
scirocco
Just to clarify, having a short torso or long legs has no effect on whether you may need a setback post or not, assuming you're talking about the same frame and same rider position. It's only if you have short or long femurs in relation to tibia length that setback is affected.
So the most important factor is the STA of the bike (because every 1 degree steeper needs about 10mm more setback to compensate). After that comes the rider's preference for where they want to be in relation to the KOPS "easy-to-measure" reference point. If you like being 20mm behind KOPS, like DaveSSS. then a setback post may be necessary even on a relatively slack 73 degree STA frame. But 20mm behind KOPS is quite a lot. I doubt most people are that far back.
You've missed the whole point of this discussion, that KOP is not considered to be relevant by many well-regarded fitters who pay NO attention to femur length. It's mostly about weight balance. Longer torsos will require more setback to achieve a proper weight balance and femur length has nothing to do with it. My saddle setback preference has nothing to do with femur length. My point is that I use a lot of setback even with a short torso and a long torsoed rider would need even more to be properly balanced.
Using a further back position can also help recruit the use of the glutes, rather than being so dependent on the quads - very important if you do a lot of climbing like I do.