A clip that can actually be measured
Your first analysis is free, with the report and the overlay video. Take five minutes over the setup; that is the difference between a measurement and an error message.
The two things that go wrong most often
Frame rate
Set your camera to at least 60 frames per second
Phones are often on 30 out of the box. At 30 frames per second and 75 revolutions per minute there are only 24 frames in a revolution, and then you are measuring the camera instead of the rider. At 60 there are forty.
Camera angle
Square to the bike, at bottom bracket height
If the camera sits at an angle the pedal path becomes an ellipse instead of a circle, the scale no longer holds, and the analysis stops. As far back as you can get with the zoom in beats close up on a wide angle.
The whole setup
- Find the crank arm length. It is usually stamped on the inside of the crank arm: 170, 172.5 or 175. This is the one number you must not guess: the entire scale hangs on it, and therefore every measurement in millimetres.
- Put the bike on a trainer with the rear axle fixed, and let them ride in for a minute. The position in the first thirty seconds is not the position someone holds for an hour.
- Camera on a tripod, directly beside the bike at the height of the bottom bracket. Filming handheld gives you a wobbling bottom bracket and with it an unusable circle fit.
- Film twenty to thirty seconds at a steady cadence. At ninety revolutions per minute that is forty-five to average over.
- Close-fitting clothing, even light. A flapping jersey turns the hip into an estimate, and a window behind the rider turns them into a silhouette: and a silhouette has no knee.
If you also want to compare left and right, film a second clip from the other side. The far leg passes behind the frame and behind the near leg, and the model then fills those points in rather than seeing them. The analysis detects that and in that case measures the drive side only: which then also goes in the report.
This is a position measurement for comfort, efficiency and performance. It is not a medical examination and says nothing about complaints or injuries.