Most amateur cyclists approach aerodynamics the wrong way. They spend £2,000 on deep-section wheels and then ride to the start line in a flapping club jersey with a helmet that's been sitting in the garage since 2017. The wheels might save 3 watts. The clothing and helmet situation is costing them 20.
Dan Bigham held the UCI Hour Record before it was broken by Filippo Ganna. He is now Head of Engineering at Red Bull-Bora-Hansgrohe, where he works alongside World Tour riders for whom a 1-watt margin can decide a race. When he joined Anthony Walsh on episode 2106 of the podcast, he was direct about what the amateur market gets systematically wrong: the hierarchy of aero gains is well understood at the professional level and almost universally inverted by amateur buyers.
This article follows Bigham's framework. Position first, clothing second, helmet third, wheels fourth, frame last. Each section explains the physics, the realistic savings, and what that means for riders doing sportives, gran fondos, or long solo efforts.
The aero hierarchy most cyclists get wrong
At 35 km/h, aerodynamic drag accounts for roughly 75-80% of the total resistance a cyclist faces. Gravity, rolling resistance, and drivetrain friction split the remaining 20-25%. That ratio shifts further toward drag as speed increases. By 45 km/h, drag is closer to 90% of the problem.
This is not a controversial finding. It is foundational biomechanics, and it explains why professional teams invest so heavily in wind tunnel time and CdA measurement. The question for amateurs is not whether aero matters, but where in the aero system the largest marginal gains sit.
Bigham's hierarchy, as explained on the Roadman Cycling Podcast, runs: body position, clothing, helmet, wheels, frame. The order is not arbitrary. It reflects the typical watt savings available at 38-40 km/h, the upper end of what a fit amateur produces in a sustained effort.
The mistake most cyclists make is inverting that hierarchy. They buy the frame or the wheels first because those purchases are visible, aspirational, and aggressively marketed. The items at the top of the hierarchy — position and clothing — require less capital but more attention. That friction is why they get ignored.
Understanding where you sit on that hierarchy before spending any money is the starting point. The aero vs weight question is related but separate: at most amateur speeds and on most amateur routes, aero has a larger return than weight savings, but the two are not always in direct competition.
Position: the biggest free gain
Body position determines CdA: the product of drag coefficient (Cd) and frontal area (A). Reduce frontal area, and drag falls with it. The rider's body accounts for roughly 70-80% of total system drag. The bike accounts for 20-30%. That ratio means every change to how the rider sits on the bike has more aerodynamic consequence than any change to the bike itself.
Bigham's view is that amateur riders routinely present 10-20% more frontal area than they need to. Handlebar height, back angle, elbow width, and head position are the primary variables. Lowering the front end by 2 cm, narrowing the elbows, and dropping the chin can save 10-20 watts without any equipment change at all. That is the equivalent of roughly 3-5% of the output of a rider producing 300 watts.
The limiting factor on position is comfort and power output. A position that saves 20 watts aerodynamically but costs 15 watts in power due to hip flexor restriction and breathing impairment is a net negative. This is where professional fitting matters. Bigham is explicit that pure tunnel-optimised positions only work on riders who have the mobility and strength to sustain them. At Red Bull-Bora-Hansgrohe, position work happens in parallel with conditioning work to extend the range of positions a rider can hold over time.
For an amateur doing a 5-hour sportive, sustainability is the constraint. The lowest position you can hold for the full duration at race effort is the right position, not the lowest position you can hold for 20 minutes on a static trainer. Getting a proper bike fit from a qualified fitter, ideally with some form of pressure mapping and video analysis, is the single highest-return investment available before touching any equipment.
It is also worth noting that time trial and triathlon positions compress this further. Tri bars, a reduced torso angle, and forearm support can cut CdA by 20-30% compared to a standard road position. For triathlon athletes, the bike leg presents the clearest aero opportunity on the course, provided the position does not compromise the run. That tension between aero optimisation and run protection is a core element of the coaching work Roadman Cycling does with triathlon athletes specifically.
Clothing and helmet choices that matter
After position, clothing is the next lever. A well-fitted skinsuit or aero jersey saves 5-15 watts over baggy or poorly-fitted kit, depending on the starting point. That range is wide because the baseline varies so much. A rider in a loose club jersey with long sleeves flapping at 35 km/h is losing far more to fabric drag than a rider already in a reasonably fitted race jersey.
The mechanism matters here. Fabric creates two types of drag: pressure drag from the wake behind the rider, and skin friction from the fabric surface itself. Counterintuitively, smooth fabrics are not always faster than textured ones. At certain speeds and Reynolds numbers, slightly rougher fabrics trip the boundary layer from laminar to turbulent flow earlier, which reduces the size of the separation wake. This is the same principle that makes golf balls dimpled. Some of the fastest fabrics in wind tunnel testing have a matte or slightly rough texture.
The practical takeaway is to prioritise fit over brand. A skinsuit that fits correctly — no loose material, no bunching at the knees or elbows, arms and legs covered — will typically beat a loose, unstructured jersey from a premium aero brand. Bare arms and legs, often assumed to be faster, are generally slower than covered limbs in aero-optimised fabric because skin is smooth and creates a larger laminar separation bubble.
Helmets follow similar logic. The difference between a standard road helmet and a well-fitted aero road helmet is typically 3-7 watts at 40 km/h. The caveat is "well-fitted": an aero helmet with a tail that is mis-aligned relative to head angle becomes significantly slower than a standard vented helmet. Bigham's point is that a rider who spends time optimising their head position and then wears a correctly matched aero helmet is extracting real savings. A rider who buys an aero helmet without adjusting head position may see little or no return.
What wheels and frames actually save
Wheels are the most talked-about aero upgrade and return meaningful savings, but they sit below position and clothing in the hierarchy. At 40 km/h, moving from a standard box-section training wheel to a 50mm deep-section carbon clincher typically saves 3-6 watts. A 60-80mm deep-section or disc wheel saves 5-10 watts at the same speed.
Those numbers are real. A 5-watt saving over a 4-hour sportive is approximately 2,700 joules less work for the same speed, or roughly 1-1.5 minutes over 100km at a typical amateur pace. Wheels are not a waste of money. But they are the third or fourth item on the list, not the first.
Crosswind stability is the practical complication. Deeper wheels generate more lateral force in crosswinds, which demands more steering correction and can increase rider fatigue over long efforts. The 50mm depth is often cited as the practical sweet spot for varied-condition riding because it returns most of the aerodynamic benefit with manageable handling.
Frames occupy the bottom of Bigham's hierarchy for amateurs. The difference between a modern aero road frame and a standard endurance geometry frame at amateur speeds is typically 2-4 watts. That gap has narrowed significantly as mainstream frame design has improved. In the early 2010s, the difference between an aero-optimised frame and a standard one was 10-15 watts. By 2026, mainstream road frames are already reasonably aerodynamic, and the marginal return on upgrading frame before addressing position, clothing, and helmet is very small.
The frame is also the most expensive item in the system. Spending £3,000 on an aero frame to save 3 watts when position work could save 15 watts for the cost of a bike fit is a straightforwardly poor return on investment.
The diminishing returns curve
Bigham's hierarchy illustrates a broader principle: the returns from aero optimisation follow a curve that flattens sharply after the first few interventions. The first dollar (or watt) you invest in position returns far more than the last dollar you spend on frame refinement.
This is not unique to aerodynamics. Prof. Stephen Seiler's work on training distribution shows a similar pattern: the first dose of high-intensity work produces large adaptations, but beyond a threshold the marginal return falls and the injury risk rises. The same logic applies to aero investment. The gains are front-loaded, and the expensive items are at the flat end of the curve.
Quantifying this concretely: if a typical amateur cyclist has 40 watts of total aero improvement available to them (a reasonable estimate for a rider going from unoptimised to fully optimised), the breakdown might look like this. Position improvements account for 15-20 of those watts. Clothing and helmet together account for another 8-12 watts. Wheels account for 5-7 watts. Frame accounts for 2-4 watts. The first two categories — both of which cost less than a mid-range wheelset — represent 55-75% of the total available gain.
The implication for equipment purchasing decisions is clear. Before buying wheels, address clothing. Before buying wheels or clothing, address position. Before spending anything, understand which item in the hierarchy is currently your biggest source of drag.
This is where measurement matters. You do not need a wind tunnel to get useful data. Outdoor CdA testing using a calibrated power meter and a consistent course with minimal wind is a practical option that Bigham endorses for riders without professional team budgets. Software tools that calculate CdA from power, speed, and elevation data have become reliable enough for directional testing. The goal is not lab precision but the ability to compare configuration A against configuration B under controlled conditions.
Practical aero for sportive riders
Translating Bigham's hierarchy into a practical action plan for a rider doing, say, a 160km sportive produces a clear sequence. Step one is position. Get a bike fit with video analysis and, if possible, some form of CdA estimation. Establish the lowest sustainable position for your target duration and effort level. Do this before buying anything else.
Step two is clothing. Replace any baggy or loose kit with a well-fitted skinsuit or aero race jersey. Prioritise arm and leg coverage in fitted fabric. If budget is limited, a skinsuit from a mid-tier brand that fits correctly will outperform a poorly fitted skinsuit from a premium brand every time.
Step three is the helmet. If you are still riding in an old round-vented helmet, an aero road helmet matched to your head angle saves 3-7 watts and costs £100-250. That is a strong return per pound spent. Match the helmet tail angle to your actual riding position, not to the position shown in the marketing imagery.
Step four is wheels. A 50mm deep-section carbon wheelset is a genuine aero upgrade, particularly for courses with long sustained efforts at 35 km/h or above. The returns are real but smaller than the three preceding steps. Buy wheels after the preceding work is done.
Step five, if you are still optimising, is frame. For most amateur cyclists, frame is the last thing to address and often not worth addressing at all until everything else is sorted. An aero frame on an unoptimised rider is a poor use of money.
One final point from Bigham that applies across the whole hierarchy: consistency matters more than perfection. A position you can hold for four hours at race effort is worth more than a theoretically faster position you fade out of after an hour. An aero setup that works on every ride and every course is more valuable than one optimised for a specific tunnel condition.
If you want structured guidance applying this framework to your own riding, the Roadman Cycling coaching programme works through exactly this kind of analysis as part of a personalised plan. Getting the hierarchy right before investing in equipment is the work that actually moves the number.