Originally Posted by
Jakedatc
Modern compact frames also have to compensate for shorter seat tubes by putting the saddle further forward on the rails and/or without setback. as you raise the seat post you need to move the saddle forward to keep the saddle in the same spot. geometry people
my 90s trek has the saddle in the middle of a straight post. my 2005ish bike has the saddle slammed forward on a straight post.
That is completely wrong. It doesn't matter whether the seat post is inside a longer seat tube or exposed above a shorter seat tube. The line is the same. The effect you are talking about only relates to seat tube angle, not the length of the seat tube. With the same seat tube angle and reach from the BB to the saddle, it doesn't matter how long the seat tube is or how much post is exposed, only the total of the two. It has no effect on saddle position. Think about it!