Cycling Power/Aerodynamics and TT

A 40 kilometer time trial is a great test of a cyclist's fitness. However, it is not sheer power that guarantees the fastest time in a race against the clock. Power moves a cyclist forward by overcoming the three main factors that resist a cyclist's forward motion: gravity, aerodynamics (wind), and friction (rolling resistance).

This past Saturday was host to the annual Wisconsin State Time Trial Championships, near Milwaukee, WI, on the famous (and flat) Double Bong TT course . Since we at CycleOps are headquartered in Madison, Wisconsin, we were able to get some power files from the Men's Pro/1/2 race to see a real-world example of how the best power output doesn't always equate to the best time.

Ryan Baumann, a Trek-Livestrong U23 rider and native Wisconsinite; Matthew Busche, local up-and-coming cat 1 racer, and Jordan Roessingh, strong cat 1 racer with a wife, a dog, and a day job agreed to provide their power files for our comparison. Let's take a look at the data and the results.

Ryan Baumann chose to race with no special aero-equipment. He raced "Eddy Merckx" style with a road bike, a road helmet, Bontrager Aelous 5.0 (50mm deep) wheelset, and a skinsuit. He weighs 74 kilograms and is about 2" taller than Busche and Roessingh. He turned out an impressive power average of 400 watts (5.41 watts/kg).

Matthew Busche raced with a time trial bike (Trek Equinox 7), a rear disc wheel, a Bontrager Aeolus 9.0 (90mm deep) front wheel, a time trial helmet, and a skinsuit. He weighs in at 70 kilograms and is the same height as Roessingh. Busche's average power was 347 watts (4.95 watts/kg). It is also relevant to note that Busche lost about 30 seconds by riding off course mid-race.

Roessingh is the same height and weight as Busche and used all the same equipment as Busche - the only difference being that he used an Bontrager Aeolus 6.5 (65mm deep) front wheel. He averaged 271 watts (3.87 watts/kg) for the 40 km distance.

Any guesses at who finished first?

In the end, the riders' times for the 40 kilometer course were as follows:

Busche: 0:50:57
Roessingh: 0:53:33
Baumann: 0:53:47

While Baumann had the largest power output by far, Busche came in with the fastest time by a large margin, winning the State TT with the best time on the day. The combination of his high average power and full TT gear was enough to propel him to a 29mph average, and a smoking time of 50:57, despite the detour

Looking deeper into their performances, though, is more revealing. Jordan's time deficit to Busche was only 2:36, while his power deficit was a huge 76W. His relatively small time loss was due to the fact that Roessingh had a more aerodynamic position on his bike. Given their weight, speed, and power, we can calculate how aero (the product of their frontal area and coefficient of drag) each rider was. For example, if Roessingh wanted to be able to match Busche's time, his superior position meant that he would only have had to produce about 315W, more than 10% less power than Busche put out. Baumann, on the other hand, was a comparative sail, as he would have had to put out almost 470W to match Busche.

This comparison is a great illustration of how big of a difference TT gear and body position makes in putting together a great time trial. To Baumann's credit, holding 400 watts for nearly an hour is a monumental achievement for a cyclist, and with his 1292 kJ's of work (compared to Busche's 1061 and Roessingh's 872), one could certainly argue that he got the best workout that day.