Malachi Cashmore Pro triathlete - BTA Watt Savings explained

The graph below shows the difference in power required to overcome 45kph measured every 3 degree increments of yaw. For this test every yaw angle was individually measured for 30 seconds in duration. The yaw angle represents the direction of the apparent headwind. E.g. 0 degrees yaw represents a straight-on headwind and 9 degrees of yaw represents significant cross winds.

One point worth mentioning is that testing in an indoor velodrome (in contrast to this test) only tests aerodynamic performance at extremely low yaw angles which doesn't represent 'real world' out door conditions in terms of typical side winds of an exposed bike course. We mention this because Absolute Speed products are designed and tested to perform well across all yaw angles. Aerodynamic performance in cross-winds is just as important (if not more important) than aerodynamic performance at low yaw angles. On a bike course like Ironaman Kona, Ironman Arizona & Ironman Chattenooga, a very significant portion of the time is spent at high yaw angles. More info can be found on this subject in the following Slowtwich article: Real World Yaw Angles - Slowtwitch News

On a side note, the reason the graph isn't perfectly symmetrical is mostly due to the drivetrain making the bike slightly asymmetrical.

The best watt savings Malachi saw in this test was a 19.5W saving @ 9 degrees of yaw. He also saw a saving of 12W @ 0-degrees of yaw and an average saving of 9.1W across all yaw angles.

BTA Aero Testing at Silverstone Sports Engineering Hub Wind Tunnel

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Josh Lewis Pro triathlete - BTA Watt Savings explained

The graph below shows the difference in power required to overcome 45kph measured every 3 degree increments of yaw from -15 degrees to +15 degrees. For this set of results below, every yaw angle was individually measured for 20 seconds in duration (slightly shorter than normal due to Josh's very impressive standard deviation). In other words, Josh's body remained extremely still while he was pedalling throughout the testing session making the data very repeatable and also exceptionally reliable; the dream pedalling 'manikin' for wind tunnel testing! One point that's not mentioned enough in wind tunnel testing is a very low standard deviation is very much what you are looking for when trying to consistently detect marginal gains.

With Josh we tested 3 different BTA setups compared against a baseline of no BTA (the pink line). The 'regular' single bottle BTA (the blue line) was approx. 2-4W faster than no BTA. The Absolute Speed double BTA in a low position with (the lower bottle being an aero bottle) (the red line) saw an average watt saving of approximately 6-8W across all yaw angles and the same Absolute Speed BTA raised higher up with 4x additional 10mm spacers saw an average aerodynamic saving of 9-11W across all yaw angles.

Although every athlete is unique (as there are so many different variables from one athlete to another), a noticeable pattern in common we have now witnessed with many athletes in the wind tunnel is that the more you can close gaps between the rider and the bike so that both in effect becomes one, the better the aerodynamic performance and the lower the cda. Strategically positioning hydration between the arms and under the chest helps close gaps and helps the re-direct wind flow around the body rather than straight into it. Positioning a bottle between the arms not only provides a rider with additional hydration but can also provide an aerodynamic advantage over not having the BTA. A double bottle between the arm also provides very easy access to much needed hydration. The faster you can access your hydration, the longer you can spend in the aero position.