Blog · 3 October 2026 · 2 min read
A kilo lighter or an aero helmet? What’s worth more on your course
Weight is the upgrade everyone understands. You feel it every time you pick the bike up. Drag you can’t feel at all, so most riders spend on the wrong one.
A kilo or a helmet, on three courses
Here’s one rider, 75 kg on a 9 kg bike holding 200 W normalised, on three IRONMAN 70.3 courses from the library. Once with a kilo less on board, once with an aero road helmet, which the site puts at 0.007 m² less drag area than a vented one.
On Eagleman, the flattest of the 123 IRONMAN 70.3 courses in the library, the kilo is worth about 10 seconds. The helmet is worth about a minute.
On San Salvador, the hilliest, with 1,341 m of climbing, the kilo finally starts to count: about 40 seconds. The helmet is still worth more, about a minute.
Why the air wins
Weight costs you mostly when you’re climbing, and on most courses a climb is a small part of the day. Drag costs you everywhere you’re going fast, which on a triathlon course is nearly everywhere.
Two honest caveats
Two honest caveats. This is the same rider at the same watts, and losing a kilo of yourself isn’t always free: some riders lose power with it, some don’t. And a helmet only saves what it saves on someone shaped like you. A time-trial helmet saves more in the aero position and can be worse than a road helmet once you sit up.
The predictor prints these for any course: what a kilogram is worth there, and what 0.01 m² of drag is worth. Check your own course before you spend.