Originally Posted by queerpunk

that's very cool.

for anybody who doesn't know, Stack and Reach are the two measurements that remove other geometry variables so that you can actually compare the sizes of two different bike models.

Consider this: a bike with a black frame and a lower seat-tube angle and a red frame with a steeper seat-tube angle are next to each other. because of the seat-tube angle, they have very different top-tube measurements - but regardless of that, you still need to put the saddle in the same place to get your saddle:bb relationship correct!

the Reach measurement measures from a vertical line coming out of the bottom bracket, to the middle of the headtube - so it removes the effect of a variable seat-tube angle.

Stack and Reach are the ONLY way to compare the sizes of bikes.