Plumb your numbers it into best bike split and see what it says

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Full-time Engineer / Part-time Pro Triathlete
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I just did this for a friend. With NP = 277 a disc is 53 seconds faster than wheels with 30mm rims which are 300 grams lighter. If you're afraid this will keep you from the podium go for the disc, otherwise use whatever's more convenient. I leave my disc at home this time.

Make sure you've tried 10% climbs and long descents with that rear disc. If you're confident with those, then I'd say why not.
Some disc wheels are at risk of rubbing against the rear derailleur so check that's not the case because you'd lose any gain.
Very few seem to choose a full disc wheel at IM Nice but I've seen at least one in June.

Ayant déjà fait le parcours avec disques (Trek Madone) et sans disques (Trek Speedconcept), je n'ai pas constaté de différences de temps notables, MAIS s'il pleut, vous gagnerez beaucoup de temps sur les descentes qui demandent beaucoup d'agilité. et le freinage ;-)

I think the issue with the disc is actually descending vs ascending. I ride a disc with everything but I am way faster with technical descending with “regular wheels”. Technical descending will play a massive role in actually getting the biggest benefit
Of the disc which is the sail effect( you arent getting cause your braking). I am actually riding very wide wheels for the better traction and comfort even tho they are 45mm. In terms of weight , the weight difference for me for just rear wheel is over 450g which feels better climbing although probably overall is a wash.
The rear derailler thing can be an issue too. id say comfort level plays a role. In other hilly courses that have long easy descents such as st george, disc 100% of the time.

This has been THE QUESTION of late.

I've consulted with a 2 pro's and 3 AG over that issue. Most are going with 60front and 60-90mm rear. I really haven't advised anyone to run a disc mostly for handling issues.

You might be overall a bit faster on the course with a disc. I think when you remove the modeling and go to the bike handling skills section that modeling doesn't/can't take into account, I think/suspect most will be more comfy and therefor faster and probably safer with a deep rear.

Hard to finish a race optimally if you crash at 55kph on a descent. Plus who needs that?

Hope that helps

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

I’ve actually been worried more about the descents as well. I used to live in Hong Kong so my bike handling skills while descending are quite decent. However, I do remember descending a hilly race one time with a disc and with the extra weight of the TT bike, my bike descending skills went out the window. Had a few poo my pants moments before i decided to really slow it down.

So after consulting with a few more people, I’ve gone from 81/Disc to 81/81 to now a 55/81 setup which coincidentally was my setup in Kona.

There are a few like me who probably would prefer no disk but are riding same set up as Lahti. As pack fill doesn't make much difference to my result anyhow

It would be interesting to see what the saving for a disc are if we assume no benefit for descents >3% (on the idea that bike handling, not aero drag, will be the speed limiter).

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