The custom Bike Aero Data calculator allows you to take the guesswork out of modifying your aerodynamic position to ensure that you can take advantage of the free performance gains that might be available to you.

Using nothing more than some readily available information about you (and your bike) and some sample ride data, you can use our FREE calculator to:

  • Calculate your CdA
  • Estimate your performance potential

How do I use the calculator?

Well, you will need some basic measurements like your weight and the weight of your bike. We also have to plug in a few coefficients like rolling resistance and drive train efficiency (don't worry there are default values you can use).

You will also need some sample ride data - distance, speed and power.

Collecting good sample ride data:

  • You could use a race file, but any sample ride data in your chosen position will work. Don't be tempted to just select a personal best performance - it is much better to chose ride data from a carefully selected route under specific riding conditions
  • A nice flat short circuit course is recommended, or if you need to ride an out and back course - then perhaps pick a flat route of a couple of miles to and from a roundabout (for easy turning). Try to ride traffic free to avoid any draft effect
  • The ride should be done on a nice calm day at as close to a constant power as possible - the calculator takes no account of wind, so sample data from a windless day will provide more accurate results
  • It's worth taking the time to collect some good sample ride data - as they always say with data "rubbish in, rubbish out". You will probably want to repeat your measurements in several different positions, so pick your course wisely.

Dr Robert Chung who has pioneered this method of estimating CdA from power data (the "Chung Method") has provided more information in his excellent paper on the subject:

 

Once you have the data, plug the numbers into the calculator and click 'calculate'. This will work out an estimate of your CdA (and Cd if you have also been able to provide a measurement of your frontal area) as well as your performance potential. You can then change various variables to see how your potential might change at different weights, for different power values or in different riding conditions.

 

The results can then be used alongside a determination of your frontal area to perform a more in depth analysis and to establish an estimate of your Cd value. This will allow you to compare different positions and setups in order to make measurable, quantifiable gains. When comparing positions it is, of course, a good idea to repeat you sample data rides on the same route.

Again it is possible to calculate an estimate of your frontal area at home with just a few photographs and some readily available computing tools, but it can be a little tricky - try googling how to do this, but don't worry it's not critical if you consider CdA as a single constraint in your calculations.