Originally Posted by
guadzilla
The problem with using Reach at a fixed height above the BB is that if I have my bars at a substantially different height, then I will need to re-calculate the reach as applicable for me - and the same HTA-induced error margin applies here as well. So I may gain consistency, but the numbers become less intuitive.
The HTA has only a tiny effect... they are all ~72.5 +-1 degree. It's the HT *length* that has a large effect... *if* you are measuring at the top of the HT.
I think you still misunderstand. If you take the Reach at a fixed height above the bottom bracket, and you have determined that a frame with 400mm Reach gives you the correct extension with a -6 110mm stem, then this will be true of every 400mm Reach frame you look at. You won't need to screw around with adjusting for HT length (or Stack), to figure you what the proper stem length would be.