Originally Posted by
brawlo
Yes but no.... Reach is taken horizontally from the BB to the top of the head tube at the centre of the steerer. You can then look at the head tube angle if you want to get more specific, but the reach and stack dimensions are the absolute best ways to compare frames to each other. Essentially, after you are correctly fitted, your saddle position is fixed for height and setback. If you want longer, you need a frame with more distance to the bars i.e. reach, or shorter being the opposite. If you want a higher handlebar setup, higher stack, or lower stack for the opposite.
If a 56cm frame with 140mm headtube has the same Reach as a 50cm frame with a 100mm headtube, do they actually have the same useful reach?
If I buy a frame with a particular Reach and install 30mm of spacers, is the reach the same as with no spacers?
Reach, as defined, is only useful if you are going to use the bike with no rise, or if you are comparing bikes with the same stack. Outside of that it is useless number that makes short head tube frames appear to have long reach, since they don't account for the increased set back of the angled seat tube.