Aero Analysis

 

The Aero Analysis screen is the engine room of BikeMetrix. This is where you can analyse all your test rides to gain accurate metrics on your different ride configurations. BikeMetrix supports several different testing methodologies, which are summarised below and explained in detail in the app Help screens.

Testing your ride configurations allows you to establish the following metrics:

BikeMetrix supports 6 different aero analysis modes.

Virtual Time using GPS and power sensor data

BikeMetrix plots the actual ride from your loaded file, and then overlays a predicted plot that uses the GPS distance / elevation and power meter data from your ride and predicts the time to complete each data point in your ride. In other words, elevation and power are fixed, and time is predicted.

Picture showing Virtual Time using GPS and power sensor data analysis mode

Virtual Elevation using GPS and power sensor data

BikeMetrix plots the actual ride from your loaded file, and then overlays a predicted plot that uses the GPS distance / speed and power meter data from your ride and predicts the elevation change for each data point. In other words, speed and power are fixed, and elevation is predicted.

Picture showing Virtual Elevation using GPS and power sensor data analysis mode

Coast Down using GPS data

BikeMetrix plots the actual ride from your loaded file, and then overlays a predicted plot assuming no input power, using GPS data.

Picture showing Coast Down using GPS data analysis mode

Virtual Elevation using speed and power sensor data

This is the most accurate mode. The procedure is the same as for Virtual Elevation using GPS above, but uses a speed sensor for distance rather than GPS.

Picture showing Virtual Elevation using speed and power sensor data analysis mode

Coast Down using speed sensor data

Another flavour of Virtual Elevation testing assuming no input power, using a speed sensor rather than GPS for greater accuracy.

Picture showing Coast Down using speed data analysis mode

Tabular lap analysis

A generic report on all laps in the ride showing different metrics and averages. Useful for quick comparisons, for example if you are doing repeated runs on a segment and want to quickly test something out without the more stringent test conditions needed for other modes.

Picture showing Tabular data analysis mode

In addition, BikeMetrix can model the effects of wind during analaysis, and enables you to slice and dice your ride files to remove parts where the test conditions were affected by things such as braking, uneven wind, poor road surface and so forth. You can very quickly chop out the parts you don't want.

BikeMetrix uses laps to mark the boundaries of different test segments. So for example, you can test on a half pipe course, going out and back multiple times, and at the start and end of each test run you hit the lap button. At each end of the half pipe, you can use your brakes or even stop your bike completely because when you hit the lap button at the start of the next segment, you know that the 'turnaround' lap can be removed from analysis.

This means you don't need to find a perfect loop or half pipe that you can ride without braking to test on. As long as you know which parts of your ride were the test portions where you didn't use your brakes, you can chop out the noise during analysis.

You can flip between analysis modes with a click of the mouse.

Removing Bad Data

In GPS modes, BikeMetrix can be set to automatically detect and compensate for anomalies that exceed a configurable threshold of error, allowing you to cope with braking, gusts of wind and poor road surfaces. This makes it very simple to get good metrics even when conditions are not ideal. Anomaly Detection can be turned on or off via the preferences screen.

Which method should I use?

If you don't have a power meter, using one of the coast down methods can get you accurate figures for CdA and Crr, but not for drivetrain efficiency. Some recumbents lose some power due to boom flex and longer chainlines that results in a lower overall efficiency, so you should bear this in mind if using coast down analysis.

Virtual Time testing is great for longer routes where you can minimise the effects of GPS innacuracies by using base map data and corrected elevation from your cycling app such as Strava. It enables you to get a very good 'real world' set of metrics for a given configuration, where all the road condition variations and GPS innacuracies are smoothed out by the length of the test segment. This gives you good metrics for race planning where you have a similar level of accuracy in your input data file for the plan.

Virtual Elevation testing using power and speed data is best for doing very detailed testing where you want to test small differences between different setups. It will give you a more accurate overall set of metrics, but some of the detail may be lost in the noise if you try to apply these figures to longer routes when planning.

In summary - coast down testing is good if you don't have a power meter. Virtual Time and Virtual Elevation testing complement each other - use Virtual Time for real world numbers over longer distances and Virtual Elevation for more accurate numbers over shorter distances in a more controlled testing environment.