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Is a disc wheel worth it? About two minutes on a 70.3, almost anywhere3 October 2026 · reading it nowA rear disc and a deep front wheel save our rider about 2 minutes on the flattest 70.3 in the library and about 2 minutes on the hilliest. What the predictor can’t price is the one thing that decides it: the crosswind.
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Blog · 3 October 2026 · 2 min read

Is a disc wheel worth it? About two minutes on a 70.3, almost anywhere

A disc wheel is the most visible upgrade in triathlon and the most argued about. Here’s what it’s worth in minutes on real courses, and the one thing the minutes can’t tell you.

How much time does a disc wheel save?

The site puts a rear disc with a deep front wheel at 0.014 m² less drag area than a pair of box-section alloy wheels, the middle of the published range. We gave that to one rider, 75 kg on a 9 kg bike holding 200 W normalised, on three IRONMAN 70.3 courses: Eagleman, the flattest in the library, Goa, which rolls, and San Salvador, the hilliest, with 1,341 m of climbing.

On a road bike the disc saves 2:12 on Eagleman, 2:12 on Goa and 2:08 on San Salvador. On a TT bike it saves a little more, 2:47 on Eagleman, because the rider is going faster.

Why the course hardly matters

Why doesn’t the course matter? Because the disc takes a fixed amount off your drag, and drag costs time wherever you’re fast. A hilly course has slow climbs, but it has fast descents too, and they count. It’s the same reason a hilly course takes less off a TT bike than people think.

The whole time carries a give or take of about three minutes, because nobody knows your drag area without measuring it. That doesn’t make the disc’s two minutes doubtful. The same unknown sits in both times, so the difference between them is much surer than either: the table puts it at a few seconds either way.

The crosswind, which the minutes can’t price

What the predictor can’t price is the wind. It leaves the crosswind out, because what a crosswind does to you depends on your wheels and your body, and no plan knows that. That’s exactly where a disc earns its reputation, good and bad. In a gusty crosswind it’s the deep front wheel that moves you around, and a race you can’t hold a line in is a race you won’t spend on the aero bars. If your course is known for it, that’s worth more than two minutes, and it’s your call.

Price your own wheels

To price wheels against what you ride now, the aero page puts them on the ride you’re planning, beside a helmet, a skinsuit or a position.

What the predictor said, with and without the disc

What the disc saves on a road bike, course by course

Eagleman, flat2:12 faster

Goa, rolling2:12 faster

San Salvador, mountain2:08 faster

A model, not a measurement. What it can show depends on the numbers above (what you typed, and what your files recorded) and on assumptions this page states; anything it cannot stand behind says so rather than drawing a tidier line.

A rear disc and a deep front wheel, three courses

	Eagleman · flat, 91 km, 3 m up	Goa · rolling, 92 km, 334 m up	San Salvador · mountain, 90 km, 1,341 m up
Road bike	2:44:38	2:55:10	3:19:11
Road bike with the disc	2:42:26 · 2:12 faster, ± 0:06	2:52:58 · 2:12 faster, ± 0:06	3:17:03 · 2:08 faster, ± 0:07
TT bike, sitting up above 5%	2:28:13	2:38:56	3:03:41
TT bike with the disc	2:25:26 · 2:47 faster, ± 0:10	2:36:09 · 2:47 faster, ± 0:10	3:00:54 · 2:46 faster, ± 0:12

The disc and deep front wheel at 0.014 m² less drag area than box-section alloy wheels, the aero page’s figure. For a 75 kg rider on a 9 kg bike holding 200 W normalised, harder up the climbs and easier down them, in still air and with no stops: the predictor, asked on 3 October 2026. The give or take on a saving is what a drag area taken off a list rather than measured could put it out by.

Try the disc on Eagleman