Speed Lab

The Speed Lab features helps you analyse aerodynamic changes to make you go faster!

Ride the same route twice, change one thing, your position, wheels, helmet, clothing or tyres, and Speed Lab estimates the aerodynamic drag (CdA) for each ride and reports the difference. 

What you need

A power meter, a GPS head unit, and two rides saved as .FIT files. Garmin, Wahoo and most other head units all work. Ideally the two rides would be carried out on the same road with similar weather conditions, but this is not essential. The perfect scenario would be an out-and-back route that has a few hills where you will ride at a variety of speeds. Ideally no sections where you need to drag your brakes. You do not need to ride at exactly the same speed or power, but keeping things reasonablly similar does help improve results. 

Running an analysis

1. Do a baseline ride and a comparison ride, changing only one thing between them.

2. Import both .FIT files into the app.

3. Tell the app about your setup: bike type, riding position, clothing, road surface and tyres.

4. Run the analysis and review your results.

5. Provide feedback in the App to help us improve the algorithm.

Getting a good result

Accurate system weight is important: stand on the scales with your bike just before you set off, and enter that figure rather than an estimate. Beyond that, ride the same route both times if you can, with a mix of flat, climbing and descending, keep conditions similar (calm wind give the most consistent results), and change only one thing between rides.

Reading your results

Speed Lab reports the CdA for each ride, the percentage improvement, and the estimated power saving at 32kph/20mph. Alongside these you'll see confidence indicators, including R-squared (above 0.90 is consistent and reliable) and how many valid data points the analysis found, so you know how much to trust the result.

What's a typical CdA?

Typcal CdA by bike type, before position and clothing are accounted for: TT 0.25 sq m, aero road 0.31 sq m, endurance road 0.33 sq m, gravel 0.35 sq m, mountain bike 0.40 sq m.

Position makes a big difference: aero bars can take off around 0.05 sq m, aggressive drops around 0.03 sq m, drops around 0.02 sq m, while riding on the tops adds around 0.025 sq m and sitting upright adds around 0.05 sq m.

Clothing matters too, from a skinsuit at the low end to baggy clothing at the high end. Across every combination, realistic CdA ranges from about 0.19 to 0.47 sq m.

How it works

Speed Lab pulls the weather data for your ride, temperature, pressure and humidity, to work out true air density rather than assuming standard conditions. Wind is modelled as a 2D vector using recorded wind speed and direction, and compensation is only applied when doing so measurably improves the consistency of the result. Each ride is broken into short segments and scored for speed, power and acceleration stability; segments that don't hold a consistent gradient and direction are discarded. What's left is analysed with robust statistics that reject outliers, so a single bad segment can't skew your result.

In-app guidance walks you through preparing your rides and reading your results, and full analysis data can be exported as a CSV file.