Criterium Aero Analysis – Analysing a mass start race

I took part in my first bunch race last Saturday. It has been a great opportunity for me to understand the applications of for planning and analysing mass start races.

One especially cool thing from racing on a circuit is that I am collecting loads of aero data. Each time I cross the same point on the circuit caclulates my CdA (Aero Efficiency). So this is what I thought I’d show you here. Then you can do the same analysis for your own races. How well do you shelter in the bunch? Find out by analysing your race on myWindsock like this.

My Race’s Aero Analysis

Have a look at my CdA profile for the race…

Blue section I am in the bunch more aero than the ride average.

You can see the Blue section is where I was in the bunch. Hey look! good for me with practice I became more efficient using the bunch for shelter from the wind. I can see this because the Stepped line representing each lap’s CdA gets lower and lower. The blue represents me being more aero than my average CdA for the whole activity.

Evidently by my CdA I didn’t spend all my time on the front 😉

The Breakaway

After 20 minutes I decided to go for a breakaway and except for a couple of laps to start with, it was solo effort to the finish. You can see this on the above graph, I stop being in the Blue and my CdA is up in the shaded orange section, I am now less aero than my average CdA. Each step in the line represents my CdA for a lap. I am happy that I was pretty consistent at keeping my Aero Position.

My solo break. My CdA is super consistent! All those years of time trials.

Overall Aero Stats

So how did my aerodynamics change from the Bunch to my Solo Break. Using the conditions on the day I have also used myWindsock to estimate Watts to lap the Salt Ayre course at 25mph.

CdA Watts @ 25mph
Full Race 0.238 315
In the Bunch 0.188 265
Break Away (Solo) 0.264 350
Crossing the line.

One more thing… Braking Analysis

In the below picture you will see the Detected Braking graph. Interestingly I only used the brakes when in those first 20 minutes when in the bunch. Braking is taking away your energy. By attempting to reduce the amount of braking by being less reactive when riding in the bunch may be away to further conserve energy. This is just a thought.

The red bars are braking instances. I only touched the brakes when in the bunch.

Analyse your  rides and races

It’s easy to access your ride’s CdA and analyse with myWindsock. You can connect Strava to and view all your Activities and Segment efforts immediately. Or simply upload your ride file to Get started here.

Look for some pre-race weather and analysis? Check out the British Cycling Event forecasts before your next race.

Author: bnorbury

Ben Norbury is four times Manchester & District Middle Distance and Best All Rounder Time Trial Champion from 2016-2019. During this time he developed software to eliminate uncertainty of the weather conditions out of his pre-race preparation.