See if this helps:

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Alex Arman

Strava

I think the Plasma 3 and Plasma 5 are different?

Reading’s hard. I’m dumb.
Nothing to see here....

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Alex Arman

Strava

I used to have one and I think the stack was around 500mm if I remember correctly. I am also 5'9 and had a medium. It is a long and low bike and I remember it being just a hair on the long side for me back them as I was not in that aggressive of a position. Now I would probably ride a medium as my position is a lot more aggressive.

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Andy Mullen
Team Zoot

stack is just vertical distance from top tube to BB center, correct?

if so measurement "F" in their geo chart (510 for S; 540 for M) multiplied by cos (14 deg) should give you the stack, or 49.5 and 52.4, respectively.

personally i'd recommend the size S. I'm 174 cm with an inseam close to yours, and that's what I ride (albeit on the TT version, which has an absurdly small HT length). You'll likely need to use quite a few spacers on the aerobar though

try this thread: https://forum.slowtwitch.com/...ch_and_Fit_P3031311/

I also think on the front page somewhere, probably about 8-9yr ago, there is a stack/reach chart on ST for this bike. Not sure if it's in a stack reach article of the articles they wrote when the 3 came out

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Brian Stover USAT LII
Accelerate3 Coaching
Insta