effective top tube length
The effective seat tube length is the distance between the bottom bracket and the point at which a virtual horizontal top tube would intersect the seat tube.
For a related dimension, see Effective top tube length.
The effective top tube length is the horizontal distance from the top tube/head tube junction to the seat tube. This measurement has become significant as more and more bikes are designed with sloping top tubes.
Effective top tube length is one of three options for defining the length of the front triangle. For more on this, see here.