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Disclaimer: I'm pretty committed to the weirdness of the build, essentially going for Keegan Swanson's Stigmata in theory but with front suspension, flatbar, and aero extensions (prob bar yak). function: bikepacking, adventure riding, with the ability to handle modest to moderate singletrack on normal road spaced hubs. I run a generally aggressive fit. Getting caught up with some geometry numbers so:

My current bike has:

-17deg. 120-130mm stem (depending)

40c-c drop bars, hood grip position about 110mm north of stem center

72deg HTA + 51mm rake, 40mm tires for 62mm trail

This puts steering offset at 230-240

Speccing the new build's cockpit around some nice titanium parts i've had lying around, could modify if need be but i'd like to keep them (bar and stem) in:

-12 degree 120mm stem

740mm flat bar with 5deg backsweep

~70deg HTA + 50mm rake, 50mm tires for 80mm trail

This puts steering offset at 107

Will be running the FOX32TC 50mm suspension/50offset

Ive read about flat bar to drop bar conversions and how, overall, the stem length doesn't really need to be changed that much, see: https://torstenfrank.wordpress.com/2...ie-und-praxis/

But since I'll be building up a new custom frame, wondering what modifications one would make to general geometry. For instance, I know i'll have longer chainstays to afford clearance, and was planning on a slightly longer ETT than my last build to run the slightly shorter stem and improve balance. But a bit lost around all the reach measurements.

From some light cad drawings i can tell that the flat bar hand positions will put me at an angular distance (shoulder to grip position) of only about 10-20mm less than the hoods/flats on my current bike, after accounting for the 10mm increase in TT length that I want to make from my current frame, which seems pretty good.

Anyway, if anyone has experience in what worked for them going from drop bar to flat bar geometry (without translating that full on to the geometric demands of a proper XC/Trail bike, but rather creating a mutated version of the two), please chime in!

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  • I've recently bought a new stem and flat handlebar and had to do some calculations to reduce the reach and increase height. Since the style of my bike is Vintage, I am limited to what is available with quill stems and did go though the process of looking a my frames head tube angle and then stem angle and length, just to find that there are online web calculators that would have save me time drawing. I've never built a frame before but maybe this webpage can be of help. Also once in the webpage click on the yellow exclamation mark next to the "Fit" for read more bikestem.fit
    – MindDBike
    Commented Aug 30 at 13:14

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