Last week, we published a blog all about how myWindsock calculates your cda from the data that you collect while you’re out on your bike. If you’re a consumer of cycling media, like us, or find yourself having a chat to your mate who has been in the wind tunnel recently, you might have noticed people saying “my cda is [insert number]”. This can be a little confusing, because although you get “average cda” when you look at a ride in myWindsock, you see that your cda graph looks something like this…

During the blog on how myWindsock calculates your cda, we looked a little into the origins of where this formula comes from…

All of these variables in this equation, are themselves functions of something else. Power is a function of time (unless you do an exactly evenly paced ride of course, then it’s constant). Air density is a function of altitude and weather and speed is a function of many things but changes during the course of the ride too. All of these variables are known at each point on the ride and cause cda to be different at each point in time.

It’s currently the case that you can use the myWindsock advanced settings when making a forecast to enter a speed or gradient dependent cda – something that may reflect you sitting up out of the TT bars over climbs and getting back into position on the flatter segments. This will change soon, but more on that in the future.

The key thing to remember is that your cda is not a fixed number, but a parameter which constantly changes and has many dependencies feeding into it. The best time trialists and triathlon cyclists have a sixth sense for minimising it at all times. Narrowing their shoulders, shrugging their heads and staying in the TT bars even during slower parts of the course.

If you want to know your cda while you ride, sign up to myWindsock here.