Marc Graveline is an aerodynamics consultant who works with WorldTour cycling teams as well as professional (e.g. Chelsea Sodaro, Lionel Sanders) and amateur triathletes, and road and gravel cyclists. He co-developed the Notio Konect, the first consumer on-bike aero sensor, and now develops his own device, the Gizmo. He also led the testing programme behind IRONMAN's decision to move the professional draft zone from 12 to 20 metres.We cover how to run an aero test you can actually trust, what to test and in what order, tyres and tyre pressure, and what IRONMAN's draft-zone testing actually found.