Disc Wheels in the Wind

So I know that a disc wheel actually makes the bike more stable in windy conditions (by virtue of shifting the pressure centre of the bike, and presumably via an gyroscopic effect vs a normal wheel).

However, at what wind speeds do people tend to forgo a disc in favour of a shallower rear (and appropriately matched front)?

Disc no matter the wind, just change the front if needed.

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Wanted to resurrect this thread… from what I have seen it’s pretty universally recommended that no matter the wind the rear disc is the way to go… my question is, is there a speed below which it’s not worth it? I’m scheduled to do the celtman and the run is so brutal I want to go real easy on the bike, around 160-170 watts. Based on elevation etc this should translate to an average speed of 17-19mph.

Is it still worth running a rear disc at that relatively low speed?

Never, I might go with a shallower front but since I got my disc (4years ago I think) I’ve used it in winds gusting up to 33mph. I probably wouldn’t race any wheel if it was worse.

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The only time I would not use a disc is if I raced Kona…and only because it isn’t allowed.

Even when I did the 70.3 WC in Chattanooga, which had a long sustained climb up Lookout Mountain, I ran a disc.

All disc, all the time…unless you are in Kona.

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There certainly is a speed, where a disc wheel is not worth it. But before that, you should go from Tri-Bike to road bike.
A disc wheel might be 400g or heavier than a comparable shallow rear wheel. If the rider/bike/Food/spares system weighs a rather low 80kg, that is a saving of 0.5%.
So that is the amount of power you are likely to save on a steep climb (300W vs 301.5W).
On everything that isn’t sub 10mph, you will save far more than that with the disc wheel.
I don’t think, that there is a single iron man/ challenge course in the World, where a rear disc isn’t the fastest option.

Lighter wheels are only faster on straight up hill climbs in time trialing.

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Chris Froome won the mountain TT in the tour a few years back riding a disc…they are always faster…as mentioned you can swap out the front for a shallower wheel if its windy…if it’s to windy to ride a disc on the rear it’s to windy to race. I only weigh 61kg and have never had problems with a disc in a TT - had problems with a 90mm front occasionally though! :grimacing:

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I wonder what speed Pogacar was doing at the end of the final TdF TT last year. He switched to a road bike for the finish and won (So I guess weight outweighed areo at that speed), although the benefits of a TT bike/disc was superior before he switched :thinking:

The difference was that the TT ended on a climb, so yes, weight beats aero in that situation. But even then, I have serious doubts about the time lost for the swap vs. time gained due to the lower weight…and it is more than just straight math. It is the physiological cost of getting going again after going all out and stopping, finding your rhythm, etc.

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I’ll be riding a disk at Celtman. Mainly because it makes that great whomp whomp whomp noise :rofl:

There’s potential to be blown off your bike by a big gust if you’re crawling up the steep climb out of Gairloch, moving at 2mph, but otherwise disk all the way.

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lol… thats all i needed to know… disc it is for me as well then… hopefully this weather lightens up and it isn’t 2 degrees C at the start of the race. That will not make for an enjoyable bike ride with all of the winter kit on

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Well, that climb was La Planche des Belle Filles, with gradients of up to 20%. At those kind of gradients, it is not just aero v weight, it is also a matter of getting the raw power out when the bike is that inclined. Most riders switched from TT to road, and put out more power on the climb. Dumolin was one of the few who chose to ride the TT bike up the climb (he is generally acknowledged to climb well on a TT frame), and put out more power on the flat than the climb.

Climbing at 7% on a TT bike is different from climbing at 10+%. But there aren’t that many TT climbs that are that steep.

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The decision to swap bikes for a climb like that makes sense imho.
While aero always matters and the heavier bike is not crazy much heavier, the power and comfort on a road bike are quite a bit superior. If Poga and Rog figured they can produce 10 or even 20 watts more on an RB, and also have maybe one kg less to carry, it might well be worth the less aero bike and the even the addition time required swapping the bike.