In that case it's because they are holding on to an old sizing regime (for no good reason I can discern).
Thanks to my penchant for amassing frame geometry it has become clear that it's really not uncommon for the reach/stack progression to be all over the place. Not many brands have realised what these metrics allow them to do with designing a size range.

I think it was Mark explained that their philosophy is to use shorter and shorter stems on the small sizes to get the reach you need, so as to reduce the degree of toe overlap that would be created by actually shrinking the reach of the frame.

Perhaps some of the other geometry properties are chosen so that handling remains good with shorter stems on those smaller sizes?

---

---

Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Ok, and I realize it was Mark that said this and not you, but why change the seat post angle? In order to keep my rear end and knees in the same relative position to the bottom bracket I would just have to slide the seat back on the rails. If I changed how I was related to the bottom bracket according to the seat post angle and given the constant chain stay length all the way up to the 56 wouldn't that move my center of gravity more towards the front tire versus someone who was larger on a larger frame? Maybe that is also why they want a shorter stem, slow down the handling from the increased front weight percentage. There are a bunch of inter-related things here and I'm just trying to understand how they got to where they are. It makes sense to me how Cervelo/Felt makes small frames, change stack and reach proportionately, and fight toe overlap with fork offset and appropriate head tube angle (simplifying but not by much). Just trying to figure out the reasoning behind a different method.

I don't know why seat tube angle would change.
Does that happen all the way up and down their sizes, or just on the ones where reach stop changing?

---

---

Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

It appears that the bigger you are the more they are going to put your rear end over the rear wheel, they start lengthening the chain stays in the 2 biggest sizes.

It is interesting, top tube length grows pretty steadily from small to big, but reach barely grows at all (and barely none at all for the bottom 3 sizes). most of the front to back adjustment is being done via Seat Tube Angle.

I would love to hear Slowman's or Mark's opinion on why you would/would not do this.


For reference I have included the Venge's Geometry chart.(ok the original chart looked good in the editor, not so much in the forum itself)

http://www.specialized.com/us/en/bikes/road/venge/sworks-venge-duraace-di2#geometry

Remember to take head tube angle into account. So if you are looking at 2 frames with the same reach but one frame has 20mm more stack then for a given stem clamp height the shorter bike will have in the neighborhood of 8mm less reach (x distance from dan's articles). But I still see you point, that's a lot less change in that dimension compared to frames in bigger sizes.