Commentary, further detail and references for Streamlines Tyre Testing Methodology. Each note is addressed by name so it can be cited from anywhere in the Knowledgebase. Working draft, 2026-10-05.
The first two assumptions are part of the Virtual Elevation method. The third is not in the paper that sets the method out.
That paper is Robert Chung's "Estimating CdA with a power meter", in its version of March 2012. It presents the virtual elevation profile as "a handy diagnostic for whether the model assumptions are met", and it calls a control run with a base configuration on each outing "good experimental practice". It does not say that repeat runs are unnecessary.
The view that the residual is a sufficient check, so that a result can be given without comparisons or repeat runs, is a later one. Robert Chung set it out on the Performance Process podcast in February 2025, and has repeated it in online forums.
It matters here because of what follows from it. Where the view is held, repeat runs are not reported, and without them there is no measure of repeatability to set beside the Streamlines figures.
The 2012 paper does give one figure for the precision of Virtual Elevation, a CV "as low as 0.3%". It comes from a single set of data. The CdA that closes the virtual elevation was found for each of about 500 consecutive, overlapping lap-length intervals, and the figure is the spread of those values once their systematic component is removed. The paper notes the strong serial correlation between them, so they are not independent repeats. The figure shows how consistently the equation closes within one ride; it is not the repeatability of a measurement.
Chung R (2012). Estimating CdA with a power meter. Version of March 2012. anonymous.coward.free.fr/wattage/cda/indirect-cda.pdf
Mc Laughlin R, Fretz C (2025). The Chung Method explained: How to aero test in the real world. Performance Process podcast, Escape Collective, 5 February 2025. escapecollective.com
Referenced from: Virtual Elevation (Chung method)