"This piece was written in 2016. Alex has since confirmed that his power for the hour was 358w, not the 395w his team claimed. Our analysis still stands, albeit with it likely that Alex has more power available than predicted. We will be doing an updated piece nearer the event to breakdown what it will truly take to beat Campenaerts at sea level." - Dan Bigham
Last week Alex Dowsett announced he was going to go for a second hour record attempt after Bradley Wiggins put a huge 1589m on to his old record. I had previously done some maths on Dowsett’s record to see what power he was putting out and what he might be able to achieve in the future. Now he’s announced a second attempt and is confident he can take the record back, I’ve decided to revisit the maths and see what is required to overhaul Wiggin’s 54.526km.
Since I last crunched the numbers Movistar have released Dowsett’s power data from his hour record set in May 2015. Unfortunately, it wasn’t released as a complete power profile rather, just an average power for the hour: 395w. Taking this value along with multiple variables taken from the day and interviews we can calculate Dowsett’s CdA, as well as what proportion of his power output was spent on accelerations, drivetrain, rolling resistance and aerodynamics.
The atmospheric conditions were taken as 26.5 degrees’ Celsius air temperature and 1007mBar air pressure, giving an air density of 1.160kg/m3. Comparing this to Wiggins hour record, where he experienced around 30 degrees Celsius on average with air pressure of 1036mBar, giving an air density of 1.176kg/m3. To put this in context, if Dowsett had ridden in the same conditions as Wiggins he would have required another 1.38% power output to maintain his 52.937km/h. This might seem small, but another thing to consider is Wiggins had to increase the air temperature significantly to compensate for the high air pressure. This increase in air temperature would have definitely taken its toll on Wiggins physiologically, resulting in a lower power output.
Dowsett did the hour record on Continental Tempo Track II tubulars, versus Wiggins on what look to be a custom compound of the Vittoria Pista Evo CL. Unfortunately, I don’t have any Crr (coefficient rolling resistance) values for the Continentals, however general opinion is that they don’t roll quite as well as the Vittorias. I do have some roller derived Crr values for the Vittoria Pista Evo CL, which came out at 0.0017. I have therefore assumed the Continentals to have a Crr of 0.0020 - a reasonable assumption.
Dowsett also appeared to run a standard chain with no wax optimisation and also ran typical sized chainrings. In comparison, Wiggins ran a Muc Off ‘nano’ optimised chain and rode with a large 58T chainring to reduce chain tension. Unlike standard chains and chainrings, this combination could save 1.5-2% of total power output.
Taking all of these factors in to account we can calculate Dowsett’s CdA, which comes out at 0.1905m2. From this we can then break down his performance in to its constituent drag sources:
Total Power: 395w
Aerodynamic Power: 351w
Rolling Resistance: 30w
Acceleration: 2.5w
Drivetrain: 11.5w
If Alex was to ride Wiggins hour record of 54.526km on the same bike in the same conditions he experienced back in May 2015 he would have to increase his power output by 36w, requiring 431w to complete the distance. This is a huge power increase at world class level, and is likely beyond the reach of Dowsett, even in peak form. If we are to look what TT power data Alex has released since the record, we are able to get an idea of what he might be capable of. When he broke the UK 25-Mile Comp Record early this year, Alex averaged 409w for 44:29. It stands to reason that with good training in the lead up to the second hour record that he might be able to sustain this power output for a further 15:31.
Having knowledge of this power output, we can start to consider what equipment changes and conditions could put Wiggins’ hour record within reach of Dowsett. Firstly, let’s assume he gets some superb atmospheric conditions with a low air pressure of 1000mBar and an optimum aerodynamic-physiology balance of air temperature of 28 degrees Celsius, giving an air density of 1.145kg/m3. This would bring the required power output down to 425w, still a little out of reach.
Next, let’s say Alex fits some Vittoria Pista Evo CL tubulars, lowering his Crr from 0.0020 to 0.0017. Dowsett now only needs 420.5w to match Wiggins. Optimising his drivetrain with a WattShop DirtyFast waxed chain alongside some oversized PEEK carbon-fibre chainrings from Pyramid Cycle Design could increase his drivetrain efficiency to 98.5%. Now Alex needs just 414.5w to draw level with Wiggins - but this is still a bit too much to ask.
The final, most crucial, value that Alex can work on is his CdA. It is well documented Alex spent significant time in the wind tunnel prior to his first hour record however, it was also stated there were compromises made for comfort. Since then Alex’s two major backers have made noticeable developments on their equipment: Canyon and Endura. Canyon have released an updated Speedmax time trial bike and Endura have a new silicon bead trip technology that has been employed by the Movistar pro cycling team over the past season. If these two key components can reduce Alex’s CdA from 0.1905m2 to 0.1880m2 then the required power output is now just 409.5w. Breaking this down to its constituent drag sources:
Total Power: 409.5w
Aerodynamic Power: 374.3w
Rolling Resistance: 26.5w
Acceleration: 2.7w
Drivetrain: 6w
To throw a curveball in, let’s see how Dowsett and Wiggins could’ve done at altitude. Going to altitude has some major benefits and also some negatives. At altitude, the air pressure is much lower, therefore reducing the air density. The extent of this is massively noticeable (air density can get as low as 0.90kg/m3) giving a directly proportional decrease in aerodynamic drag. 10% lower air density means 10% less aero drag or 2.15% (10^1/3) faster. However, the decrease in air pressure negatively affects the aerobic power the athlete can produce. Bassett et al have done studies to assess the effect on available aerobic power to both non-acclimatized and acclimatized athletes, at 1,000 feet intervals up to 14,000 feet above sea level. Using these percentage decreases of aerobic power, we can calculate the power the athlete will have available to them, and then calculate the distance accordingly. If Dowsett was to go to Aguascalientes Bicentenary Velodrome in Mexico at 1887m above sea level with great conditions, giving an air density of 0.930kg/m3 and ensured he was fully acclimatized there on a completely optimised bike and a 409w FTP at sea level, he could achieve an amazing distance of 56.662km. This would put over 2km on to Wiggins record and also take Chris Boardman’s all-time record of 56.375km set in the superman position prior to the UCI Lugano Charter that brought along the unified hour record in 2014. However, had Wiggins decided to go to altitude for his record then he would take the mark to a huge 57.167km. I can’t see anybody toppling that any time soon.
To quote Alex - "We just want to get that record and do it in the most conservative, risk-safe way as possible. We're not interested in putting on a big old show because it's a big mark. But it's in me. The numbers show that it's in me." It’s true, the numbers do show that it’s in him. I wish Alex the best of luck in his next attempt, I really can’t wait!