October 27, 2020 in Support

This document serves as reference for technical terms and jargon used throughout AeroLab’s products and documentation.

Sections and Laps

A section a continuous stretch of the course where CdA calculations are performed. Sections are the building blocks which compromise a laps.

A lap is defined as the distance travelled by a rider from the starting point of a test back to the starting point.

For example, for an out & back test there are two sections per lap (the out and the back). Whereas, a circuit course such as a velodrome a single section is equivalent to a lap since there is no turn around.

Combined Weight

The mass of the rider and all equipment (bike, helmet, clothes, ect) worn on race day. Best practice is to measure all together as it introduces minimal error.

Wheel Circumference

The distance in millimeters traveled by one revolution of the wheel. The quantity is used in the on-board calculations within the AeroPro. To reduce error averaging multiple wheel rollout tests is suggested. Error in wheel circumference is corrected in any outdoor protocol, absolute accuracy is only required for indoor testing such as a velodrome.


A converged CdA value is the goal of an aero test; a good indicator of this is observing consistent values across multiple laps within a session.

Wheel Rollout Test

The test performed to measure wheel circumference.

  • Mark or align with a feature (i.e. logo or valve stem) the point on the tire in contact with the ground;
  • Roll the bike forward 1 or more whole revolutions of the wheel;
  • Measure the distance from the starting to end location of the wheel contact point;
  • Divide by the number of revolutions performed;

Example: If 5 revolutions measures a rollout of 10.48 meters the average wheel circumference is 10,480mm/5 = 2096mm

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