There is no magic to this. Give us your watts per kilo and target RPM at say 90% FTP on the steepest grade in your race and you have the answer to the gearing you need for a half IM. This is independent of 1x or 2x. Just calculate the gear inches at target wattage for that grade.

My 2 cents is your 50x28 is insufficient if your steepest grade is anything more than 6% in a half IM. Its certainly going to be too large a gear for a full IM. For an Olympic depending on the length and steepness of the grade "maybe".

Can you tell us your watts per kilo?

W/KG when I’m in race shape is 3.6 to 3.7 range. I would say cadence on steep grades would be around 60.

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Favorite Gear: Dimond | Cadex | Desoto Sport | Hoka One One

60 seems low for a steep climb unless standing out of saddle, but we all have different riding styles. My gut feel is you need 48x32 for Olympic and half IM tri, but if you get a long hill like 2km long over 7% you're going to be bogged down.

By the way, I have been testing exactly what you're asking about on a 40km TT loop that has 800m of total climbing keeping it in the big chainring (50) with a large sprocket of 32. I actually don't access the 50x32 and stop at 50x28 due to cross chain. This course has several hills that are 6-10%. I'm right around the same as you hovering in between 3.6 and 3.8W per kilo. I feel 48x28 would be a stretch, but 48x32 would be fine on this particular course. The course at IM Tremblant is not as hilly (900m over 90km), but its steeper parts are steeper. Its probably doable on the 12-14% grades with a 48x32 for you and I for the half IM, but for the full, I think we would pay on the run.

I have been doing this type of testing because I was looking at gettting a 1x Dimond and wanted to make sure that I can get enough gearing in a 1x for my watts per kilo.

You’re right granny gear cadence probably much higher. I haven’t seen a hill in years. 😁

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Favorite Gear: Dimond | Cadex | Desoto Sport | Hoka One One

Anyway, my 2 cents is that you're probably OK with a 48x32 for almost all courses if you're at 3.7W per kilo minute some really climbing oriented courses like the old Vegas 70.3 World's, Wildflower, St. Croix, Tremblant 140.6, Nice. You'd definitley be fine in Kona on a 48x32....50x28 you may be in trouble. By the way, which 1x are you looking at getting. I have not rode my bike that much this year aside from 5 hilly rides and only taken it out of the big chainring for 2 of those rides (the other 3 I decided to hammer and crank as they were 2 hr rides so I could empty the tank).

I already have 1x on my TriRig Omni. SRAM eTap AXS with 50t chainring and 10-28 cassette. Was looking to put 1x on my Dimond but have decided not to.

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Favorite Gear: Dimond | Cadex | Desoto Sport | Hoka One One