Aerodynamic Testing

What it is. Direct drag measurement at the Silverstone Sports Engineering Hub. You and your bike are held on the tunnel platform in smooth, uniform airflow — set to your racing speed, with speed sweeps available all the way to 80 km/h — while a force balance measures aerodynamic drag directly and a turntable sweeps you through the yaw angles your event actually produces. Unlike typical tunnel systems, we can also vary yaw dynamically mid-run: a more realistic test, and high-fidelity yaw data gathered far more rapidly. CdA is computed run by run, corrections applied, live throughout.

Best for. Equipment and position decisions where crosswind behaviour decides the answer — wheels, helmets, frames, fabrics. Speed sweeps that map how a setup behaves across your full racing speed range, from steady TT pace to 80 km/h.

Why it’s valid. The tunnel is the only venue where drag is measured directly — a balance reads the force itself rather than inferring it from power and speed — and results are repeatable to a fraction of a percent. It’s also the only venue where we control yaw. Real-world wind almost never hits you dead-on, and equipment and positions that win at 0° can be worse at 10°: we sweep your event’s yaw range, statically or dynamically, and weight the results into one honest, event-correct number.

Honest limitations. We can match your race power on the platform — but constrained riding can’t reproduce the dynamics of the open road: the inertia you pedal against, and the way your body supports itself when the bike is free beneath you. That doesn’t invalidate tunnel results; it’s why they pair so well with a velodrome or Catesby session, where the position is proven under real riding dynamics.

Sessions. Day: 2 h £1,475 · 3 h £2,175. Evening/weekend: 2 h £1,175 · 3 h £1,725.

What it is. A 2.7 km purpose-built indoor straight road inside a sealed Victorian railway tunnel — laboratory-stable air you ride your own bike through at race power and race speed. The surface is extraordinary: less than 5 mm deviation from true across the full 2.7 km, on a constant, precisely known 1-in-176 gradient — flat, smooth and identical on every single run. We test with the Streamlines Cirrus system: out-and-back runs with extremely high-resolution CdA on every pass.

Best for. TT and triathlon riders validating position and equipment at true race intensity. Riders without track experience — it’s a straight, flat road, so line-holding is never a data problem. High-speed work: the constant gradient means the downhill direction enables very high test speeds — invaluable for road sprinters, capturing repeatable race-speed CdA at speeds impossible to sustain lap after lap on a velodrome. Immediate feedback after every run on how a change actually feels to sustain.

Why it’s valid. Catesby is the rare point on the spectrum that’s high on measurement confidence and realism at the same time: a sealed working section keeps conditions consistent for assured repeatability, while the riding is completely real — dynamic pedalling, real inertia, full race power. The CdA we measure is the CdA you’ll race with.

Rail-tunnel aero testing is unique to WattShop — no other UK provider offers it. It’s also where we do our most demanding work: the combination of the tunnel’s controlled environment and the Streamlines Cirrus system produces exceptionally clear aero data.

Honest limitations. Still air — near-zero yaw, so equipment crosswind sensitivity belongs in the wind tunnel or a Cirrus field test.

Sessions. 3 h solo £2,425 · 3 h paired £2,650 · 4 h solo £3,125 · 4 h paired £3,350 · 4 h triple £3,350 — support mechanic included on shared sessions.

What it is. Real-road testing with the Streamlines Cirrus system — on our validated test roads in Northamptonshire and Oxfordshire, or on carefully selected roads near you. Setup takes ten minutes; you ride out-and-back or loop runs holding position and power, and CdA resolves run by run, measured to within 2 watts at 45 km/h — around 1%.

Best for. First tests, and the most cost-efficient route to a full optimisation — up to 15 setups in a two-hour session, sometimes more. Position work in a genuinely realistic environment. Equipment crosswind response in real, measured wind. Proving a controlled-environment setup out in the world. Ongoing monitoring between sessions.

Why it’s valid. The wind you race in is the wind you should test in. Cirrus measures every key variable that impacts drag performance — air speed and wind angle at the bike, elevation, speed effects, body position — and normalises for them in scientifically valid, advanced ways. This is a genuine test environment, not a compromise: you optimise your position under the conditions you actually ride in, with the measurement rigour supplied by the system. (Full system story below.)

Honest limitations. Weather-dependent — sessions are scheduled around conditions. And the one group it doesn’t suit: track riders, whose racing environment is the velodrome itself.

Sessions. 2 h £750 · 3 h £975 · 4 h £1,175. And we travel — anywhere in the world. For testing beyond our home roads, contact us and you’ll have a quote within one business day.