Originally Posted by
Russ Roth
So why does it matter more? This is the thing that's always under explained. The effective top tube is also vague but tells me if a frame is within a range of what fits. Since I ride seated knowing how far the relative distance from the seat to the stem is seems better than a number that tells me how far from the bb to the stem. I don't sit at the bb. I will agree that ett is a vague number, I've never seen it as more than a starting point, same as when toptubes were straight across. Just don't see how reach is any more effective or imparts any more info. Stack is just something good to know especially with flexibility.
You don't sit at the BB, but your feet are fixed to it and the distance from there to the head-tube is also a fixed distance. So I find reach useful exactly in the same way you and I find stack useful. Reach and stack together provide a fixed reference point to the BB. Saddle and bar position relative to those 2 points are adjustable variables. As also mentioned, when you are standing reach is all that matters as far as length is concerned. So I prefer to know what the reach is from the BB and then I know I can always position my saddle with my preferred setback, regardless of top tube length. If the reach is far too short or long, then I know I'll never be able to get my preferred saddle setback.