In between frame sizes - go up or down?

So im pretty comfortable on about a 55tt,

This is my BMCs geo, 100mm stem with about 25mm of spacers underneath

This is my Giants geo, 54.5tt with a 100mm stem and 6mm spacer underneath (bigger headtube)

This is the geo im tossing up between for the frame im currently eyeing, as you can see its its a 54 or 56

Ive had an older cannondale in a 54 with a 110mm stem and then the last cannondale which was a 56 with a 90mm stem, was much more comfy with the latter

Im leaning towards the L as the headtube is a little taller and i think a 90mm stem is fine from previous experience.

Any issues you guys see with my logic? or anything else im not thinking about? The frame is a CX frame if that makes a difference, but it will mainly be used as a commuter.

Im still nutting out details so nothing confirmed, but would appreciate some feedback

isn’t the defy your commuter? so soon and you’re onto a mash sscx!

calculate stack and reach for your known good fits and calculate stack/reach for the mash and then pick the one that gets you the closest

Jase is the king of flipping.

Always smaller. Means more seatpost extension and better stem slammage potential

damn B! didnt think the geo was that obvious! Cats out the bag now! Its actually a 2016 Zydeco, found a mob selling as frame/fork from the states and hes quoted me $100 US to post

haha Heavy, wasnt really looking to flip but one of my work colleagues mentioned hed be keen, then i stumbled across a pic of the zydeco, and here we are.

agree on seatpost extension

i kinda thought too small of a frame means smaller headtube, means slammage would be harder, whereas a bigger headtube means easier slammage?

obviously body type dependant

as much as aesthetics playing an important part, i just want to comfortably replicate my fit without affecting handling too much.

will tackle Bs approach

you can’t compare headtube between a road and cross bike. longer fork for tyre clearancezzz means less headtube. (add ~20mm to your headtube in this case which will make it very nearly your bmc.)

get the 54, a 56 with a 90mm will be shit.

ahh cheers ash, thats the kind of shit i was hoping to uncover. Would never have known that!

Conventional wisdom is go the smaller size and component up to suit. I have several times gone the other way, having generally felt more at ease on a larger frame (especially in the TT). Went the conventional route for last roadie built and am now a convert.

56 with 90 will be shit.

But most people run their cross bikes a fair bit taller than my roadies, so you might have a + rise penis stem if you go the 54.

Rode a 56cm Venge with a 90mm stem, can confirm it was shit.

tis true, but if the name of the game is matching contact points penis stems shouldnt be necessary

Smaller and long stem are you mental. Will handle like shit with anything less than 100mm