Aero-Check World Championship track Utah

The engineers from the Swiss wheel manufacturer SWISS SIDE have carried out extensive tests on the bike course of the Ironman World Championships in St. George over the past few days in order to be able to provide their athletes with the best possible aero setup.

First insight: according to the calculations, the bike route time in St. George will be about 10 minutes slower than in Kona.

Factors such as altitude profile, air density, wind direction, road surface and optimal tire pressure were included in the calculations for the extensive aero tests. Swiss Side professional athletes participating in the St. George competition include Andi Dreitz and Daniela Ryf.

The tests on the St. George racetrack were carried out with the Swiss Side CdA-Meter (which not only determines the aerodynamic resistance, but also reveals important information about wind speed and wind direction from the driver's perspective.
Jean-Paul and other athletes were on the track every day for the measurements, with the support of the engineers at home in Switzerland, further analyzes were carried out with the measurement data. For this purpose, the current measurement data was compared with the local wind forecasts, among other things.
The key findings from the tests are as follows:

St. George's altitude is approximately 1000m, so the lower air density will result in lower aerodynamic drag and therefore higher speeds than Kona at sea level. However, the St. George route is very hilly with climbs totaling 2265 meters in altitude . This is quite a bit more compared to Kona, where there is only 1386 meters of elevation gain. We calculate that the bike route time in St. George will be approximately 10 minutes slower than in Kona .

• Aerodynamic drag remains dominant in St. George , but the importance is reduced compared to Kona. A 5% reduction in drag results in a ride time reduction of approximately 3 min 29 sec (which is 40 sec less than Kona due to the additional climbs in St. George). So the aerodynamic effect in St. George is about 85% of the effect in Kona.
• The importance of the weight increases: with the additional climbs in St. George. This is basically rider dependent, here is an example for a light athlete: 1kg extra weight results in a time penalty of about 66 seconds in St. George. In Kona the corresponding penalty would be only 31 seconds. So the weight effect is about 200% that of Kona.

Summarized effects of aerodynamics versus weight:

1.6% drag = 1kg weight

• The wind was variable during the test days and also very strong on some days. The wind is similar or even stronger than in Kona, and the wind contains even more gusts.
• The best wheel setup from SWISS SIDE for the pro athletes is the HADRON2 Ultimate 800 front wheel and the DISC on the rear wheel if the wind allows it. Individual athletes may consider the 625 front wheel if the wind is too strong.
• For age group athletes, an 800/800 setup will be used provided they are strong and experienced riders. If the wind is too strong, a 625/800 setup should be considered. The 625/800 setup reduces the wind sensitivity by 25% and only has a small aerodynamic loss (1W at 45km/h. More can result depending on the wind).
• The road is comparatively rough, so lower tire pressures are advantageous. Depending on rider weight and based on 25mm tires this is approximately 1bar less than on smooth roads. This will also have a beneficial effect on plate resistance. St. George has quite a lot of debris on the road, for this reason we do not recommend a super light tire without a puncture protection layer.
• Speeds on the descents will play an important role for the pro field, high gears will be important to increase the maximum speed on the descents. We expect some attacks on the descents.
• The wind direction with the highest potential for aero performance, which results in the greatest time savings thanks to the sail effect, is from the north. The wind direction with the smallest potential is south.