|Is "setback" a worthless dimension of geometry charts?||Fez|
Jan 15, 2004 8:23 AM
|Provided you get the seat tube angle, is the setback a worthless dimension?
True setback is ultimately dictated by saddle height, so isn't the only relevant dimension the seat tube angle?
Jan 15, 2004 10:03 AM
|Depends on your point of view. Most consumers are accustomed to the seat tube angle dimension, but traditional frame builders often build a frame with no angular dimensions at all. The seat tube is adjusted to a specific amount of setback and the front-center dimension is used to adjust the head tube angle.
Some brands will have odd fractional seat tube angles, because they are angles derived from the setback.
If a frame is designed as a series of lines representing the centerlines of the tubes, then the the cosine of the seat tube angle is the setback divided by the c-c seat tube length.
If you know that you want a certain c-c frame size, then the setback dimension can provide a valuable comparison of frame geometry.
You are correct that the total setback is determined by saddle height.