For that only being about 50 feet per mile, it’s all in how the course delivers the elevation. Is it a lot of rolling non-technical terrain? Or is the elevation all in a single big climb with a very technical descent?

If not technical disc for sure. If technical, depends.

It's pretty hard to find an IM course where a disc is not an advantage. If it's 900m in a single climb, with not ability to get aero benefit elsewhere maybe.

It's pretty easy to do a napkin calc of wether it's worth it.

Take the added weight of the disc. Say 500g. Let's say there is a 500m climb. 0.5kg * 9.81 * 500m = 2450Joules.

If the disc gives you 10watts, you need 245seconds in which you have that aero advantage to overcome that 2450 Joules cost. If it's only 5 watts you need 490seconds.

Now that assumes you won't get the 500g in your favor on the way down. Most people coming down from that climb probably don't hit peak aero, they sit up a bit......when they hit say 60km/h.

If it's lots of rolling hills, you will pay the cost going up, but get the benefit coming down and the aero benefit all the way.

I’m a bit amused that it seems to boil down to the added weight of the disc wheel.
Thought it was established in the “who counts grams for cycling” thread, that weight actually doesn’t really matter that much. And how much “heavier” is your disc anyway?

My main concern would be the weather conditions.
Will it be super windy, or more of a calm race day?
Also, I personally don’t think, a disc wheel handles any worse on technical courses than a non disc wheel.
And I don’t feel it climbs any worse than a non disc wheel. 900 meters over the course of 90 kilometers isn’t really that much. I would go for the disc if weather allows.

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I love rim brake bikes!

5W seems pretty optimistic for a disc wheel over a 60mm aero wheel. Unless there were persistent high-yaw wind conditions combined with pretty high rider speed.

Thanks for all inputs.
It's quite rolling course because there are 4 laps (it's not IM brand race, just one of Polish regular ones).
https://ridewithgps.com/routes/17107570



It's hard to say what will be the weather. For now forecast says wind will be below 10 km/h.
I think I'll go for disc wheel, especially that I'm not a light rider (75kg+).

That course is no-brainer disc.

And I was the one arguing that weight matters (but mostly for roadies) in another recent thread.

When I test the pro riders I never use a disc just to make sure a gust with sail doesn't make things look better than they are. Last run, we alway put the disc on. 5w is pretty common.

Maybe they have crappy 60mm wheels LOL.

Pro riders, sure. They TT at around 50-55kph. 5-10W easy.

I was not quoting at 50kph, but I guess everyone's mileage varies. 5w is not uncommon for an AGer, IMO.