The Froome controversy is becoming a never ending story. It all started with a tweet from Amatti Pyoraily with a calculated average power of 6.1 W/kg during the  40:43 climb of La Pierre Saint Martin.

Indeed, this number is a little high but was is correct and is it really alarming? It was based on a simplistic formula from Dr. Ferrari that does not take into account the possible influence of wind (tailwind? headwind?) ,or the effect of drafting.  Anyway, this number was the start of accusations by a well-known group of negativists

Then came the number of 7.1 W/kg due to the great scientist Pierre Sallet. Absolutely ridiculous. The first thing a real scientist should do when he obtains a surprising number is to have doubts and verify his own calculations. Obviously Mr. Sallet has no doubts.

On 22^nd July Froome and Sky then disclosed the numbers from his powermeter; 5.78 W/kg

One would think this ends the discussion but at the contrary it all starts again because this number is too low and thus it must be “manipulated”.

So let us see how wrong this number may be. Robert Gesink produced 5.72 W/kg on the same climb and lost 1:27 to Froome. Nobody doubts about this Gesink number and you do not need to be a scientist to infer from this that Froome really produced  5.93 W/kg. Exit 6.1 and exit 7.1 W/kg…

So where does the difference between 5.93 W/kg and 5.78 W/kg come from? The difference between these numbers is 2.5%
There are 3 reasonable causes.
First, the very best powermeters (SRM, Pioneer etc…) will give you numbers with a possible error of 1.5 – 2 %. This is true both for the Gesink-data and the Froome data, which means that they may differ by as much as 3 % without any specific reason.
Second, the difference may partly be due to Froome’s use of a non-circular chainring.  As an example SRM computes the average power over each full revolution with the assumption that the angular velocity is constant over the revolution, which is true for any circular chainring. However this angular velocity is not constant for the Froome chainring: it is lower in the downstroke and upstroke, and higher in the dead-point zones. This adds an extra 1 – 2 % of possible systematic error.

Finally and despite all non-believers the non-circular chainring does have a positive effect on Froome’s performance. This is no place to start a detailed explanation but science has shown that a proper oval chainring is indeed more efficient than the circular one. (See the excellent papers by L. Malfait and G. Storme at www.noncircularchainring.be  )

Altogether, much ado about nothing.