Power and aerodynamics – how can you strike a balance?

Time trials are an interesting discipline and all of you reading this will likely have found yourself in a position where you’ve done one of the following… 

  1. Gone way too aggressive with your position and lost huge amounts of power 
  2. Not gone aggressive enough and been beaten by riders doing much lower watts 

Both of these two options are sub optimal and the best way to address them is a good bike fit, to convince you of its importance though we have decided to take a look at the consequences of getting it wrong on a CTT time trials course by using myWindsock to help us make sense of the data.

CTT and myWindsock

Before we do that though, a little interlude on how you can check a CTT event in the myWindsock app

All time trials in the UK are available on myWindsock, head to myWindsock and click planner where you’ll be able to click on the UK Time Trials option.

You can select between open and club events and see race conditions by hitting the ‘view event’ tab. From here you’ll be presented with a forecast that has race day (and time) conditions that you can adjust to match your own power, cda and event start time. We will now use one of these forecasts to see what happens when we get the balance between power and aero a little wrong…

What happens when we get the balance wrong?

So, armed with this new information on how we can view CTT events in myWindsock – let’s check out Reading CC’s club 10 for the 4th of April as an example. Clicking ‘view event’ we are presented with the following forecast… 

Let’s imagine our test rider can do 350W for 20-ish minutes with a moderately aggressive position. The cda we might see for this sort of position will be around 0.250±0.2 for a 70-80 kg male rider, the cda for a female would be a tad lower as women tend to be smaller so have a lower frontal area. This gives us a time of 22:32 for this 10 mile course, pretty handy. 

Our rider then makes some adjustments, goes super narrow and drops his saddle down to get as aero as possible – throwing comfort and power production out the window. Due to this, he’s suddenly limited at his maximal aerobic power, which for a rider who has a 20 minute critical power might be around 275W, but his cda is now 0.19 – let’s see what happens to the time… 

We see that our rider is suddenly 30s slower over 10 miles. Now let’s imagine our rider does the opposite and suddenly veers the other way – raising their stack really high, going wider and moving the saddle back up high to maximise power production. Imagine they achieve a 20 minute power of 370W in this scenario but suddenly have a more typical road bike cda of 0.350, what happens to the previous time of 23:03? 

Suddenly we are faced with a scenario where our rider is doing 100W more than the aggressive position yet going much slower! 

These numbers are exaggerated slightly to illustrate a point but the fact remains that a balance must be struck between aerodynamics and comfort. 

Key takeaways

  1. Time trial positioning is a 3-dimensional problem. The time you’re able to complete a course is a function of power and cda – finding the minimum of this function is essentially the art of time trialling boiled down to mathematics!
  2. 3D calculus is relatively hard in the scheme of maths, luckily myWindsock does this for you as it calculates a predicted time based on power and cda, all you need to do is play with the numbers to find the best option for you.
  3. Usually, when striking a balance between aerodynamics and power production – lean towards aero but don’t overdo it. This way you can get quite close to the optimum without being overly aggressive and risking injury.
  4. Get a bike fit… 

If you want to perform to the best of your ability at your next cycling time trial open or club event, use myWindsock to check the forecast and plan your ride accordingly. Turn data into information and race with confidence.