If you are a time trialist or triathlete, one of the benefits of using a power meter is optimizing your aerodynamics. A better position on the bike supplied with aerodynamic equipment can help you to save seconds or even minutes in a time trial.
Now I will show how you can use a power meter to optimize aero position on your bike through a simple testing procedure.
Wind tunnel aero testing: Gold standard but expensive
Wind tunnel tests are referred to as the gold standard of optimization of aerodynamics.
These wind tunnel tests are expensive, and therefore we only see professional riders use these tests to optimize their position on their aero bikes. Therefore, logically, professional riders have a significant advantage in doing wind tunnel testing. However, often it is only the classement-riders who get the chance to do these tests due to the high cost.
Don’t worry, here comes the good news. A power meter can help you optimize your aerodynamic position without ever visiting a wind tunnel or spending extra money!
Power meter: Great performance and affordable
Currently, I think SRM and Powertap are the two best power meters on the market. Using cheaper and less precise power meters is not recommended. If you don’t have a power meter, buy one or try to borrow one.
A power meter is the single best investment for a serious rider who wants to improve performance. It enables you to perform aerodynamic testing, precise analysis of power output in races and training situations, and a solid training partner/coach makes the power meter an easy choice.
Best of all, the power meter presents objective data that are not influenced by weather, hydration, stress, or any of the many parameters that affect your heart rate.
Use a power meter to optimize aero equipment
Maybe you remember how I used a power meter last summer to investigate how much bike weight costs on Alpe d’Huez? The U23 rider who performed these trials had to maintain a power output around 275w on all four rides up Alpe d’Huez. The test bike was a Pinarello Prince equipped with Shimano Dura-Ace and SRM crank.
Afterwards, I could compare the finishing times to see what you pay if you carry extra weight. Of course, you can make more precise trials than we did here, but it shows the principle of using a power meter to optimize your equipment.
Thus, after these trials, we had a picture of how much weight matters in the Alps.
When you ride up Alpe d’Huez, aerodynamics don’t play a significant role because you ride relatively slowly. However, the speed is much higher in time trials, and many serious riders perform average speeds above 40km/hr.
Thus, optimization of aerodynamics should be the primary concern if you want to improve performance without struggling with your threshold power.
Find a good location
You will need a circuit to ride fast and maintain a constant speed/power output. This is best done on a velodrome.
The main principle is to eliminate everything unrelated to aerodynamic drag. That is why wind tunnel testing of cyclists has become the golden standard procedure. Nevertheless, outdoor testing is still necessary because you will compete when you race (corners, small hills, etc.)
If you don’t have a velodrome in your neighbourhood, then you have to be a little creative to make a good course for your tests. It’s still possible, but more factors can influence your ride. Though, it gets more challenging to show minor differences.
Write a protocol
Write down all the tests and numbers you want to collect and in which order. For example, that could be the different aerodynamic materials you would like to test or different body positions on your bike.
It’s a good idea to start with a standard upset of your bike, e.g., Standard frame + standard equipment + standard body position. Then, when you want to test different setups, change only one parameter at a time. Otherwise, it gets difficult to identify what setup change resulted in reduced aerodynamic drag.
Make two rides of 1-3km with each setup. The more rides you do, the better chance you get to show a minor significant difference.
Constant power output method
When you ride on a flat road with constant power output, differences in speed are primarily due to your aerodynamics. Therefore, if you decide to use the continuous power output method, you must keep your power output as constant as possible and your desired aerodynamic position on your bike.
When you have finished one lap on your circuit, notice your average speed and power output. Hopefully, you get power outputs so close to each other that differences in average speed can be accepted due to altered aerodynamics.
Constant speed method
When you ride on a flat road with a constant speed, differences in required power output are primarily due to your aerodynamics.
If you decide to use the constant speed method, you have to keep your speed as steady as possible and keep your desired aerodynamic position on your bike. As you can see, this method is much the same as the constant power output method.
The difference is that you try to keep average speeds so close to each other that any difference in power output can be considered due to altered aerodynamics.
Constant power output or speed?
Decide whether you use the constant wattage or constant speed method. Both are suitable methods, but I will choose the constant speed method if I have to pick one. I recommend it because it gives you the possibility to use an iPod in your ear to keep a steady pedalling frequency.
When you’ve found the right gear combination, this little trick makes it easier for you to ride at the decided speed in all tests. You follow the rhythm from the music like when you are at a spinning lesson. Thus you can concentrate 100% on holding your aerodynamic position on your bike.
Riding at speeds close to your race speed is the most optimal since you can see how many watts it’s possible to save. There is, however, a slight risk that the workouts with standard setups can become quite hard intervals. This will not happen with the constant power output method.
If you use the constant power output method, there is a risk that you lose focus on holding your aero position. The positive thing is that the result is directly shown as increased speed/saved seconds.
Thus you can immediately see how much faster you will go if put on, e.g., an aero helmet instead of your standard helmet.
It’s a good idea to have an assistant help you, for example, your cycling coach, a friend, or a family member, to keep track of the data stream. Assistants can be helpful throughout the whole process.
As I said previously, we need data from two rides with each setup close to race speed. Doing tests with a distance of 1 to 3km gives you a fair chance to notice significant changes in aerodynamics.
I recommend doing more of these tests instead of more extended tests because weather conditions might influence the results (temperature, changing winds).
It is also recommended to do a few tests at lower speeds, e.g., 80 and 90% of race speed. This increases the power of your data and gives you the chance to spot trends at an early stage.
Analysis of aerodynamics
This is the exciting part of this process since you find out what works for you. You will be amazed how much time you can save with an optimized body position on your bike. Also, you have the chance to figure out how much time can be saved if you use a rear disc wheel.
Remember to look at material and body position savings because they can add up. I know it is expensive to buy aero gear for your time trial bike, but you can find out where you get the best value (watts or seconds) for money using the principles above.
Share power meter data
Feel free to share your experiences with the readers here at Training4cyclists.com. If you have some interesting observations, let us hear about them. How many watts did you save using the principles described above?
There are many benefits of using a power meter. It enables you to do aerodynamic testing without extra cost and offers a suitable alternative to an expensive wind tunnel test.
Aerodynamic tests using a power meter can help you optimize your aerodynamic position on your time trial bike or select the right combination of aerodynamic wheels/frame/helmet, etc.