Effective STA is based on a line from the bb to the top of the seat post with the saddle at a - - sometimes and average saddle height and (edit) sometimes a line parallel to the top of the head tube. The actual angle of the seat tube is not the same number on most dual suspension bikes because the seat tube is often interrupted and rarely mates with the centre of the bottom bracket shell. In this case the seat tubes meet the down tube well ahead of the bottom bracket producing a lower angle seat tube - so if your saddle height is above the median your ESTA will be lower than that suggested by the geo chart. Hope that makes sense.
May 18, 2018, 8:50 a.m. - Cam McRae
Effective STA is based on a line from the bb to the top of the seat post with the saddle at a - - sometimes and average saddle height and (edit) sometimes a line parallel to the top of the head tube. The actual angle of the seat tube is not the same number on most dual suspension bikes because the seat tube is often interrupted and rarely mates with the centre of the bottom bracket shell. In this case the seat tubes meet the down tube well ahead of the bottom bracket producing a lower angle seat tube - so if your saddle height is above the median your ESTA will be lower than that suggested by the geo chart. Hope that makes sense.