In Reply To:
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If you're happy with your current fit and spend the majority of your time in the aero position (those two should go hand in hand) APS & APR are your #1 priority. Using a +/-10 to 15mm tolerance on nominal APR in the chart, that puts you squarely in the middle of two combinations: Medium frame with 100x10, and Small frame with 100x45. It also intersects at Medium with 100x45, but unless you're
really dialled in your current APS I'd advise against it...you'd have no spacers under the pads with no place to go but up.
If basebar position is important to you, particularly if you tend to spend a lot of time cruising out in the pursuit position, the Small + 100x45 offers the best compromise vs your current coordinates. The Medium + 100x45 almost gets the basebar stack perfect, but it's also nearly 30mm further out there and remember you've got no downward APS flexibility with that one without re-stemming in 100x10....
I don't spend a lot of time on my basebars (I do that already on my road bike) but since I use the base bars for climbing off the saddle, I would like it to feel comfortable, especially since that has little adjustment flexibility.
Anyway, after analyzing both (Carl and Nick) your suggestions, the best combo for me would be a medium frame using a 100x10. That single spacer would be perfect for Ironman distances and then I could just remove it for the shorter Olympic and Half Ironman races. We'll see. I don't think the Trek dealers right now give customers the option to choose stems and I will take whatever default stem comes with the bike and just change it later on after riding it for a few months and dialing my fit. I don't mind the medium size except for having a shorter looking seatpost (by 3 cm). One thing I liked about my Ordu in size 51 was that my seatpost stood up high like a mast compared to many tri bikes that have seatposts that look only as long as road bikes.
P.
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