Originally Posted by
Russ Roth
Stack is an easily understandable thing. I've never seen a good explanation of the importance of reach vs top tube length. Care to elucidate?
Reach is measured from the center of the BB, so it eliminates the effect of different seat tube angles. Once you've figured out the reach that's perfect for you, the STA only affects your choice of seatpost setback. My ideal is a 525mm stack, 370mm reach and 74 degree STA to use a 25mm setback seatpost. If a frame has 380mm of reach, I'll need a 100mm stem instead of a 110mm. Also, reach can only be compared at one stack height. If two frames are under consideration and one has 20mm less stack, assume that 20mm of spacer will be used and subtract 6mm from the reach of that frame.